firefox is working but IE not when internet access is limited

[devilsden]

Hi guys,
In my office internet acces is limited for certain time. But I am able to use internet with firefox even in those hours it is not accessible. But for this I am using a proxy. But this proxy is not working with IE. In Firefox the authentification details (UName/PSW) are asked for the same proxy used in tools->option->advance->network->settings. (I am using firefox version 2.0.0.20 ) . But the authentification details being asked by the IE7 is for different proxy though I am using same proxy in both firefox and IE. The website I regulary visit works only with IE and is not supported by Firefox. Can somebody tell me why this is happening with IE and any solution for this?

Thanks and Cheers
Devilsden