HP UFT 12, 12.01 & 12.02 Crash during debugging phase

During the implementation of automated testing (with HP UFT 12 or 12.01 and rarely also with 11.53), during debugging, after a few clicks on F10 or F11 (Step Over and Step Into) we find that UFT crashes systematically .
With the same mode of development (we use an our internal framework), we note also that using QTP 11 or UFT 11.52 we can work without these technical problems (the tool does not crash; or if it does, it happens very very rarely, almost non-existent case).
Could someone help us out?

Thanks,
Andrea