Vista - Webcam problems..

My friend's using a dell 1500 vostro,
when she sends a webcam invitation
nobody can see them, it's also the same if she recieves them.
Sometimes when somebody does see the invite,
and she accepts it, the webcam either stops working or nothing happens,
when she goes into the webcam settings,
she can see her webcam so it's working.
She also can't send and recieve files,
and she can't use her microphone.
She has tried exitting msn and restarting it,
she's tried restarting her laptop,
and it's been going on for about 3 days now.
Does anybody have any ideas on the problem?
or how it can be solved?

thanks in advance

The first thing would be to uninstall software and reinstall and see where that gets you. Than we can go from there if need be. Generally speaking uninstalling and reinstalling software almost alway fixes issues of this nature. Printers are also notorious for this as well.