First pass observation suggests this is a problem with application registration. I would try opening a DOS shell, cd to the directory where you'll find configurator.exe (default: C:\MentorGraphics\win32) and run the command 'configurator -clean'. Once that finishes, type 'configurator' with no arguments. You should get a drop down list that allows you to select which version you want to run. Pick the one you want an click through, then try the tool. It should let you switch between the releases from tha point on, but if not try doing the -clean thing again.
I'm making an assumption that both releases are installed in the same target folder (C:\MentorGraphics) and that you have admin rights on the machine. If either one of those things is not the case, what I said above won't work as advertised. Reply to the thread and I'll give you some specifics.
Mentor Graphics Customer Support
Thanks a lot for the support. It has worked! Did exactly what you suggested and I was able to open DXD and PADS 9.5 without any issues.
Thanks very much.