This may be caused by Spyware or a problem with any third party plugin used by IE.
Removing adware & spyware
faq608-4650
Make sure your options in IE/ Tools/ Internet Options/ Advanced are correct.
Uncheck the boxes for "Install on Demand" for IE and Other programs (two boxes).
Try running temporarily with the third box "Enable Third Party Browser Extensions" unchecked and see how this goes.
"This specifies that you want to disable features you installed for use with Internet Explorer that may have been created by companies other than Microsoft.
If you encounter problems with Internet Explorer that you cannot resolve, you can use this option to help determine if third-party features are causing the problems without uninstalling the feature. You must restart Internet Explorer after turning this option on or off."
If that stops your errors, you will know where the trouble is.
This article and the program BHOcop might be useful to you.
The ability to Repair Internet Explorer does not exist in the version that ships with Windows XP. This feature only becomes available after you upgrade to a newer version. This is normal and has been this way since Windows 98 and IE4. However, you can reinstall IE in Windows XP by clicking Start, Run and entering the following command:
rundll32.exe setupapi,InstallHinfSection DefaultInstall 132 c:\windows\inf\ie.inf
You will need to have your XP CD available. You will need to redo any IE Updates too.
Using SFC /Scannow at the command prompt will help in repairing IE.