Cain,
Could you be a bit more specific, please? Assuming that you're using Internet Explorer of some flavor and you go to the View menu, are you saying that when you click on Source nothing happens? If so, there may be a problem with your TMP environment variable OR there may be a problem with the folder it points to.
If Ladi's advice doesn't work, and assuming that I understand the situation you're reporting properly, try right-clicking on My Computer. Select the Advanced tab of the System Properties dialog. Click on the Environment Variables button. In the Evnrironment Variables dialog that pops up, look in the upper window at the TMP environment variable. If you select it and click on the Edit button, you should see
%USERPROFILE%\Local Settings\Temp
in the Edit User Variable box that pops up, unless it has been altered from the default for some reason. You should check to see that the named directory actually exists and that nothing has been done with security settings to prevent the browser from using it. For instance, if the user profile under which you are logging onto the system has been denied access to that directory that might cause this behavior. (Not absolutely certain because I haven't tried it.)
The reason that IE users need to check these items when they can't view Web page source is that IE is hard coded to copy the page from the Temporary Internet Folders directory structure to the location specified in the TMP (not TEMP) variable and then open the copy with Notepad.exe.
Hope this helps.
Regards,
Jim
Side note to Ladi: I hadn't heard that advice for this problem before. Does a full TIF cache or corrupted files in the TIF cause loss of the ability to view source from within the browser? Makes sense.