We just installed Adobe Reader X. Many were getting the "cannot open in protected mode" so we applied the McAfee hotfix 613017 and added ACRORD32.EXE to the buffer overfolow exclusion as recommended. It works on most. Bust some still get the popup that it cannot open in protected mode. I removed McAfee completely and we still get the error. Is there a way to debug Reader X so I can foind out what is stopping it from going in protected mode?
First, take a look at http://kb2.adobe.com/cps/860/cpsid_86063.html#main_Unsupported_configurations an see if anything applies. 10.0.1 will be out today, where some of the issues listed here will get resolved.