Photoshop Elements 12 crashes

Hello, over a year ago I purchased Photoshop 12 through iTunes. I have used it with no problem for over a year. Now when I try to launch the application, it says "Application quit unexpectedly. Click Reopen to reopen the application." This is an endless, repeated loop. Here is the exception message detail:

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_BAD_ACCESS (SIGSEGV)

Exception Codes: KERN_INVALID_ADDRESS at 0x00000000000000b1

Can anybody give suggestions as to how I can navigate through this? Since I purchased it through iTunes, I have no copy to reinstall. Somewhere along the line, I think I got a message that said "this application was not purchased on this computer". But this is the only computer I have. Thanks for any assistance.