For one of our users, opening any PDF file by itself works fine. If any PDF file is open and he tries to open a second PDF, the computer hangs for 15-30 seconds and then when a second Adobe Reader window comes up, the document display incorrectly with lots of graphical artifacts. The first PDF file opened continues to function normally. If we close Adobe Reader and open the second PDF from before, it displays normally without problem. Opening a second PDF (any PDF at all) again causes a brief hang and then it displays incorrectly.
We have tried uninstalling Adobe Reader, deleting the Adobe folders from Program Files and Program Files\Common Files, deleting the Adobe registry keys from HKCU\Software and HKLM\Software and reinstalling version 9.4 from scratch, but that has not corrected the problem. The user indicated this didn't occur in Adobe 8.x but has been a problem since updating to 9.x. I am not willing to install such an old and vulnerable version of the program on his computer just so it will work as expected. Please let me know if there are any specific causes and/or resolutions for this problem.
Just an observation; but, the display issues you describe may be indicative of problems with the local machine's graphics device.
It turns out that it was the 2D graphics acceleration feature in Adobe Reader. The problems would go away when disabling the acceleration but went away when the video driver was updated. It would be easy to assume it was a problem with the original video driver, but it's not always such an open and shut case. It could be that Adobe Reader just doesn't properly identify what acceleration is supported before it tries to use it.