Thread was locked (understandably so I guess) so I could not reply.
Thank you for your quick answer Caarrie, indead that bug filing is
exactly what I was looking for.
Btw. it seems to be fixed for me at the moment,
i.e. so far no amount of restarting, modifying texture compression,
shaders or removing of config-files has had any positive effect,
whereas the bug used to display an erratic behviour in previous
versions.