cs3 by any chance??
this took me a few days to sort out, and it happens because of the way adobe's new licensing system works i.e. pain in the ass. the problem i had was that i'd used the beta version and it knew the beta licence had expired but even after uninstalling, licence files and registry data was still present......
Symantec anyone......
there are several things you can do, i had to do all of the things to get it working:
# Uninstall every Adobe app (even acrobat and old versions of PS or whatever).
# download and run Adobe CS3Clean Script
http://www.adobe.com/support/contact/cs3clean.html
# delete all adobe folders on c:
# run reg cleaner of your choice.
then reinstall what you want. it just takes so damn long to install/uninstall CS3 apps, it was so frustrating to get working. PS is only 400mb or so but still takes 20 mins to install on my x6800, and it makes you turn off firefox and messenger before it will install!
adobe reckons that running their CS3 cleaner tool fixes everything and that deleting the cache.db file is located in Program Files/Common Files/Adobe/Adobe PCDcache , should fix all issues but this is not true in my case.