Do PDFs open up OK in Reader by default when you click on them? It's probably simply because CS2 isn't supported in Windows Vista or 7 because of it's age, if you ran it on XP you wouldn't have a problem. There is a compatibility mode in 7 that you could try, but seeing this is a problem with it not interacting with other programs correctly I don't have high hopes for you.
Have a look at this post here for some CS2 upgrade tips. As Bob points out if you do have the money and need to upgrade now is the perfect time to do it.
I have the same issue with ID CS4 trying to open a pdf after export.
It comes with the following error: unable to view this file because acrobat was not found. check your acrobat installation
The PDF file can be opend fine using Reader.
Tried to repair Reader but with no luck.
What's the OS? Do you have Acrobat Pro installed, or just Reader? What application is set to open PDFs?
It is running on Windows 7 and it does have Acrobat Pro 8.2.6 with Reader X also. It is set to Reader should be default.
I don't know for sure, but I suspect having both Pro 8 and Reader X installed is the problem.