Hi,
Did you recently uninstall any software or particularly the .NET Framework?, and if you uninstalled some software and said yes to delete any shared dlls then it might have taken out a .NET component that is required.

and since this is happening when you are searching I believe that it is due to some spy-ware, or an incomplete removal of spyware so to remove them properly and completely, try these
Ad-aware

Spy-bot

I would definitely go ahead to do the above anyways, but also check the following keys in your registry
start--run--regedit [Enter]
NOTE: Improper use of the registry will render the system useless
Navigate to the following key: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
In the right pane there are entries you can delete unnecessary items from here.
e.g. yahoo, aim, tkbell...stuff like that.
if you are confused then post back the entries to confirm what to and what not to delete

Navigate to the following key
Navigate to the following key: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce [Located right below the previous one]
There should be no other entries than the one which says (Default) with no value.

Do the same under the following hive as well.
KKEY_CURRENT_USER

Go to start--All Programs--Startup and the only thing you really need here is your anti-virus autoprotect and everything else can be deleted.

==rohini