I have Windows XP sp2 release canditate 1 installed and did recently the update to PB 3.90.
After that F5 did not start or compile the program and F7 did not create an exe file and no error was given.
I found that the new "program execution prevention mechanism" in SP2 was the reason. (a new "security" feature from M$ to prevent users from doubleclicking on everything)
I had to manually start each exe related to PB and uncheck the "ask again" box in the "security dialog".
After that all works fine.
Maybe the PB installer/updater needs to be patched to work with XPsp2 and those changes are done automatically.
Well Pharao, that's a logical progression for an OS that constantly wants to know whether I'm really, really sure that I want to delete something.
I'm waiting for the day that my BIOS already knows the OS and asks me whether I want reconsider my intention to boot it...