What version of photoshop?
Were you running os x 10.6 before the upgrade?
Anyway photoshop cs2 won't work on mountain lion because cs2 is a PowerPC application
and mountain lion can only run intel applications natively like photoshop cs3-cc.
If you were using 10.6, then you were using rossetta, an application that allowed some powerpc programs to run on an intel mac and mountain lion doesn't have rossetta.
The current versions of photoshop available from adobe are photoshop cs6 and photoshop cc, but since cs2 is out
of the upgrade loop now, so you need to either buy the full version of photoshop cs6 or subscribe to photoshop cc.
Thank for your help R_Kelly.