internet working in ubuntu but not windows 7

I have a dell laptop with Windows 7 installed. I have a ubuntu 10.10 installed on the same computer. The Internet was working fine till yesterday on both O.S. But due to the some odd reason I could not access Internet on Windows 7 but in ubuntu it is working fine. Actually, I am using ubuntu to post this message.

I haven't changed the network setting and am using the same wi-fi. The troubleshooting centre gave this message

"Resource (web proxy) is online but isn't responding to connection attempts. The remote computer isn't responding to connections on port 3128 , possibly due to firewall or security policy settings, or because it might be temporarily unavailable. Windows couldn't find any problems with the firewall on your computer

I am using firefox on both. On both internet was working till yesterday.
I am accessing a public wi-fi network which uses 10.0.0.3 and 3128 port.
I am using Microsoft security essentials and no 3rd party firewall.

This is the first time I have seen this error. I found things about disabling proxy but my wi-fi wouldn't work without that. What to do?

Try a system restore, to a restore point just prior to yesterday.
If that fixes things than it's likely that some install (maybe even a Windows Update wireless adapter) has caused the issue.

Tried System Restore. Internet Still not working

A new development.
I uninstalled my ubuntu 10.10 and installed ubuntu 12.04LTS. wifi wasn't working on that either. Had to go back to ubuntu 10.10 to post this message.

Link to ubuntu forum discussing this
[ubuntu] wifi not working on ubuntu 12.04LTS and WIndows 7 but works on ubuntu 10.10 - Ubuntu Forums

EDIT:
Can now connect to the wifi in Ubuntu 12.04LTS. Windows 7 still not connecting...

Actually the computer is connected to the wifi but there is limited connectivity. I cannot go to any website

Without any specifics as to your System Specs, Manufacturer Name = Dell, Manufacturer Model Name, Model Number and other identifying characteristics or the Wireless Card you are using Mfg. Name, Mfg Model, Mfg. Number, etc., it is difficult to add anything of value to your problem.
I can say that in the past on some Dell Model wireless issues we've found that, evidently the driver (new versions) default to setting the "BSS Mode" to 802.11n and some have found that changing that setting to 802.11g has resolved their issues. So....

Go into device manager
expand network adapters
select then right click the problem wireless adapter and choose properties
select the "Advanced" tab at the top
In the left column titled "Property:" see if you have a BSS Mode listed. If so select it and in the right column titled "Value:" use the drop down arrow to change from 802.11n to 802.11g
OK your way back out of there and reboot and see if that helps.

This isn't well organised but I think this can give some information.
I am not sure if its all relevant or not. I found this info in my ubuntu. If there is something missing please tell me how to get it in windows and I will put it here.

H/W path Device Class Description
=========================================================
system Inspiron N5010 (To be filled by O.E.M.)
/0 bus 0KX18M
/0/4 processor Intel(R) Core(TM) i3 CPU M 380 @ 2.53GHz
/0/4/5 memory 64KiB L1 cache
/0/4/6 memory 512KiB L2 cache
/0/4/7 memory 3MiB L3 cache
/0/4/1.1 processor Logical CPU
/0/4/1.2 processor Logical CPU
/0/4/1.3 processor Logical CPU
/0/4/1.4 processor Logical CPU
/0/4/1.5 processor Logical CPU
/0/4/1.6 processor Logical CPU
/0/4/1.7 processor Logical CPU
/0/4/1.8 processor Logical CPU
/0/4/1.9 processor Logical CPU
/0/4/1.a processor Logical CPU
/0/4/1.b processor Logical CPU
/0/4/1.c processor Logical CPU
/0/4/1.d processor Logical CPU
/0/4/1.e processor Logical CPU
/0/4/1.f processor Logical CPU
/0/4/1.10 processor Logical CPU
/0/1d memory 2GiB System Memory
/0/1d/0 memory 2GiB DIMM DDR3 Synchronous 1333 MHz (0.8 ns)
/0/1d/1 memory DIMM [empty]
/0/0 memory 64KiB BIOS
/0/1 processor
/0/1/1.1 processor Logical CPU
/0/1/1.2 processor Logical CPU
/0/1/1.3 processor Logical CPU
/0/1/1.4 processor Logical CPU
/0/1/1.5 processor Logical CPU
/0/1/1.6 processor Logical CPU
/0/1/1.7 processor Logical CPU
/0/1/1.8 processor Logical CPU
/0/1/1.9 processor Logical CPU
/0/1/1.a processor Logical CPU
/0/1/1.b processor Logical CPU
/0/1/1.c processor Logical CPU
/0/1/1.d processor Logical CPU
/0/1/1.e processor Logical CPU
/0/1/1.f processor Logical CPU
/0/1/1.10 processor Logical CPU
/0/100 bridge Core Processor DRAM Controller [8086:44]
/0/100/1 bridge Core Processor PCI Express x16 Root Port [8086:45]
/0/100/1/0 display Manhattan [Mobility Radeon HD 5400 Series] [1002:68E0]
/0/100/1/0.1 multimedia Cedar HDMI Audio [Radeon HD 5400/6300 Series] [1002:AA68]
/0/100/16 communication 5 Series/3400 Series Chipset HECI Controller [8086:3B64]
/0/100/1a bus 5 Series/3400 Series Chipset USB2 Enhanced Host Controller [8086:3B3C]
/0/100/1b multimedia 5 Series/3400 Series Chipset High Definition Audio [8086:3B56]
/0/100/1c bridge 5 Series/3400 Series Chipset PCI Express Root Port 1 [8086:3B42]
/0/100/1c.1 bridge 5 Series/3400 Series Chipset PCI Express Root Port 2 [8086:3B44]
/0/100/1c.1/0 wlan0 network Centrino Wireless-N 1000 [8086:83]
/0/100/1c.2 bridge 5 Series/3400 Series Chipset PCI Express Root Port 3 [8086:3B46]
/0/100/1c.2/0 eth0 network RTL8101E/RTL8102E PCI Express Fast Ethernet controller [10EC:8136]
/0/100/1c.4 bridge 5 Series/3400 Series Chipset PCI Express Root Port 5 [8086:3B4A]
/0/100/1d bus 5 Series/3400 Series Chipset USB2 Enhanced Host Controller [8086:3B34]
/0/100/1e bridge 82801 Mobile PCI Bridge [8086:2448]
/0/100/1f bridge Mobile 5 Series Chipset LPC Interface Controller [8086:3B0B]
/0/100/1f.2 scsi0 storage 5 Series/3400 Series Chipset 6 port SATA AHCI Controller [8086:3B2F]
/0/100/1f.2/0 /dev/sda disk 320GB WDC WD3200BEVT-7
/0/100/1f.2/0/1 /dev/sda1 volume 39MiB Windows FAT volume
/0/100/1f.2/0/2 /dev/sda2 volume 13GiB Windows NTFS volume
/0/100/1f.2/0/3 /dev/sda3 volume 152GiB Windows NTFS volume
/0/100/1f.2/0/4 /dev/sda4 volume 131GiB Extended partition
/0/100/1f.2/0/4/5 /dev/sda5 volume 131GiB HPFS/NTFS partition
/0/100/1f.2/1 /dev/cdrom disk DVD+-RW TS-L633J
/0/100/1f.3 bus 5 Series/3400 Series Chipset SMBus Controller [8086:3B30]
/0/101 bridge Core Processor QuickPath Architecture Generic Non-core Registers [8086:2C62]
/0/102 bridge Core Processor QuickPath Architecture System Address Decoder [8086:2D01]
/0/103 bridge Core Processor QPI Link 0 [8086:2D10]
/0/104 bridge Core Processor QPI Physical 0 [8086:2D11]
/0/105 bridge Core Processor Reserved [8086:2D12]
/0/106 bridge Core Processor Reserved [8086:2D13]
/1 power DELL 4YRJH11

Install the latest driver for your Intel Wireless adapter from here Support for the Intel® Centrino® Wireless-N 1000 give it a minute to completely load the information.
When you connect your computer to the network using the Wired Realtek adapter do you have the same problem?

Due to some reason wifi started working in window 7 for 1 day. I installed the latest driver as was suggested.

Then the wifi itself was down for 1 day.

Today wifi started and the problem came back. Not working in WIndows 7 but working in Ubuntu.

When you connect your computer to the network using the Wired Realtek adapter do you have the same problem?

I just use university's wifi. No wired connections.