If this just happen System Restore is the easiest way to get it back to working condition.

If that is not an option you can try System File Checker which will replace any corrupt system files.
http://www.anzwers.org/free/xpdsl/sfc.htm

Since it affect I.E. browser if the above doesn't cure it you can try the following:

* Quit all programs that are running.
* Click Start, and then click Run.
* Type regsvr32 urlmon.dll, and then click OK.
* When you receive the "DllRegisterServer in urlmon.dll succeeded" message, click OK.

If this does not resolve the problem, repeat steps 2 through 4 for each of the following files (in step 3, replace Urlmon.dll with each of the file names below):
* Shdocvw.dll
* Msjava.dll
* Actxprxy.dll
* Oleaut32.dll
* Mshtml.dll
* Browseui.dll
* Shell32.dll (Windows XP and Windows 2000 only)