Internet explorer has encountered a problem and needs to close ,,this message comes up when i try and log in to facebook and some other sites please help me with this thanks hannah

Without knowing the exact code in the message, it wiould be difficult to fix properly; however,
let's fix it this way:
Un-install IE7 or Install iE8

Install iE8:
http://www.microsoft.com/windows/internet-explorer/worldwide-sites.aspx

Hi,
You can reset the IE to defaults:

1. Open Internet Explorer.
2. Click Tools, and then click Internet Options.
3. Click the Advanced tab.
4. Under Reset Internet Explorer Settings, click Reset.
5. Restart IE settings

It is a known issue with the Internet explorer for which there is no guaranteed fix. Still you can try by removing IE7 from Add/Remove and switch back to IE 6.
Alternately you can Switch to Mozilla firefox by downloading the latest version from www.mozilla.com

Actually, I solved the problem, jeevan is right, delete all cokies and download hijackthis by trnedmicro.

This is due to the buffer overflow. Delete all cookies, temporary files.