Dear Andy,
thanks for your respond and sorry for the delay!
first: the Task Manager shows me DayZ has been closed, no process's still running.
The problem occurs only on the desktop, the taskbar and the only way solving the prob is the TM via Ctrl+Alt+Del (second mouseclick responds - after that all is fine)
second: my problem is getting more curious...
the effect of no resond on mouseclicks stays for longer (i tried waiting for 5 min) an exception is only the running steam programm. in that i can start DayZ again (as said, no process of DayZ is still running after i quit it) but with some new issues (f.e. beeing kicked to the desktop after clicking the "I understand" button - DayZ's still running)
What i've tried so far:
System: 64bit Win7ultimate, Steam installed on 2x SSD in RAID0, library on 2X HDD in RAID0, 16Gb RAM, 4x3,6GHz CPU... and so on...
Thanks for the help
Slim