I have found the culprit...

Acrobat 9 (reader and pro) do not play well with Redirected Folders in an Active Directory environment. More specifically... a redirected "Application Data" folder.

Any of my users which do NOT have roaming profiles (aka redirected folders) have no problems running acrobat 9. In other words, users who have their "Application Data" folder in "C:\Documents and Settings\username\Application Data" are fully functional and do not receive the C++ Runtime error.

Perhaps the Acrobat developers will have a fix for users of the new millenium who use UNC paths...

Hope this helps