Hello. This issue has been reported several times already, but I can't reproduce it locally. Gerd, can you please take a look, maybe you may ask better question to the OP(s) about what to try.
https://bugs.launchpad.net/qemu/+bug/1033727 http://bugs.debian.org/683983 Gerd, I tried to catch you on irc for several days, but you appears to be a non-frequent guest there these days... :) Thanks, /mjt