Windows Explorer "Runtime Error"

[Charlie]

In Windows XP Pro, when non-Administrator (Power Users)
attempt to open Windows Explorer (or search, My Computer,
etc.), they get Error Message of "Microsoft Visual++
Runtime Library"; "Runtime
error!"; "Program=C:\WINDOWS\explorer.exe""; "This
application has requested that thte Runtime terminate it
in an unusual way. Please contact the application's
support team for assistance"

THe problem developed about a month after installation
and Windows Explorer works fine with "administrator"
privilege.

Any ideas?