There are so very many things that could be causing this, it's impossible to say. I assume you are running anti-virus and have checked for spyware (using something like Spybot). There are a few things you can check. One common problem seems to be if you're running the Google toolbar or other third-party plugins that can cause IE6 to freeze (for instance, the Google toolbar will contact Google when you're loading the page, and that could hang things). Your browser may not be handling javascript well and hanging on some bit of js.
There's an interesting liturgy of troubleshooting
here dating from 2002 to 2008 (so these problems go on and on for users of IE6--a good reason to upgrade to IE7 or FF 3 or Safari for Windows).
You may have luck if you try to repair IE from the control panel:
Repair on Windows 95,98,ME, NT, or 2000
If you are using one of these versions of Windows then Internet Explorer 6 was not installed by default when you installed the operating system but rather from an upgrade. Since you upgraded to IE6 you have the advantage of having a repair tool that came with the installation.
To access this repair tool you should follow these steps:
Click on Start, then click on Settings, and then click on Control Panel.
Once the control panel window is open double-click on the Add/Remove Programs icon.
You will now see a screen that shows a listing of all installed programs on your computer. Scroll down till you see Microsoft Internet Explorer 6 and Internet Tools.
Double-click this entry and a screen will appear asking what you would like to do.
Select the option to Repair Internet Explorer and press the OK button.
Then press the Yes key to begin the process.
When it is completed reboot your computer.