Windows Vista Context Menus Not Working

I am having an intermittant issue with Vista and its menus. I have a user
that for one reason or anohter cannot open anyting in vista. when I right
click on "network" for example, it displays a context menu but when i select
"properties" nothing happens. If I just try to open for example "network",
then again nothign happens. This is only intermittant and I cannt seem to
find the source. Anyone else had this issue??