amigos,
I just heard the information from friend at Siemens,
If any of you installed PCS7 V8.0 SP1 Upd1 and used new module drivers which install OB_DIAG1 V7.2 in your project, this can cause your CPU to never start when you do entire download; the block OB_DIAG1 V7.2 will cause an infinite loop when called from OB100.
The best to use OB_DIAG1 V7.1 to solve the problem.
Be aware!