Photoshop is an evil little toad...! That or you are having an issue specific to your system, of which of course we can't know anything since you haven't bothered to provide even some basic system info, much less detailed info about the configuration, PS preferences and crash logs...
The function I tried to use seems to be named "focus selection" in English.
Sorry I missed the information about my computer etc. It is an rather old machine, 2 Years old, i5 CPU, 8 GB RAM, 2*500 MB HDD. Windows 7. So I think I havet to buy a a new computer or go back to GIMP. The simpliest and cheapesdt solution seems to return to GIMP.
I have the same problem - I have a pc windows 7 - 24 gigs of ram.