I had this problem with the beta versions of Vista, not sure about the RTM version but I have just checked SP1 and it’s OK. Do you have SP1 installed?

Here are two items to look at for errors:
1. Look in Event Viewer. Go to Windows Orb (Start) > All Programs >Administrative Tools, right-click Event Viewer then ‘Run as Administrator’. Double-click the error then the Details Tab below it to see the error information.
Lots of good information here http://www.computerperformance.co.uk/vista/vista_event_viewer.htm

2. Look for application failures. Click the Windows Orb (Start) > All Programs > Administrative Tools > Reliability and Performance Monitor > Reliability Monitor in the left Pane > Application Failures in the main window.