I have that problem too. And couldnt find any reason for it.
Also that problem disappears by it self! and come back again without no
installation no change on computer.
Also found out common thing happening with this problem is a big list of
software and windows usual services. Such as;
Firefox, MSN, Windows live, Solitaire!, Winamp, adobe flash, all microsoft
games comes along with the vista.
Searched many places, most possible solution is:
* Run as administrator. (it solved my problem for 2 weeks than didnt work
again)
* system restore is NOT a solution. because its not about updates or installs.
* some people says windows wants to shift users to windows live rather than
msn.
But than why firefox, solitaire and other programs crashing?
* sending problem report doesnt give any answer which i have 327 reports has
been made and still no results

checking solutions takes my 15 minutes

)
* * * still trying to find solution but i can only guess it is about
administrative previlages and system management accounts bla bla...