Start Menu Shortcuts Not Working

I did some digging and found some situations that sound similar to my problem, but none covered the same issue I'm seeing. I've been running Vista for several months now. At some time in the last week or two, many of my Start Menu shortcuts have stopped working. If I look at the properties of those shortcuts, it seems to be the ones that don't have an actual path in the Target field. E.g. Word as "Microsoft Office Professional Edition 2003" instead of an actual path to WINWORD.EXE, and that shortcut doesn't work. Nothin happens when you select it. However the shortcut to Notepad has "%SystemRoot%system32otepad.exe" in its Target field, and it works just fine.

This only happens with SOME of the shortcuts. E.g. the "recently used" list of shortcuts in the Start menu does this, and if I type WinKey-WORD and select the Microsoft Word shortcut that shows up there, it doesn't work. But if I select the Word shortcut under Start -> All Programs -> Microsoft Office, it works just fine -- even though it also has the non-path Target field. What has happened to these "special" shortcuts? How do I fix it and prevent this from happening again?