This is likely not a bug, but may be due to the OP reassigning the Ctl or the Alt key in Keyboard Layout. For example, changing the left Alt key to produce ISO_Level3_Shift is one of the choices with which to produce a EuroSign on a standard US English keyboard. The Ctl-Left Alt key combination then fails to release the Qemu mouse/keyboard grab -- and so it should. All of this can easily be checked with xev.
-- Henk Koster "Behavioral axioms are right, but agents make mistakes." Attributed to L.J. Savage -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]