Hi Michal!
as it looks like MSIE 6 has problems with $cfg['OBGzip'] set to TRUE, how about disabling it as default?
I've mentioned this once or twice on the forums/tracker, and I'm positive on disabling it. It seems as if MSIE6 with the a 27xx patch (I don't remember the number) corrupted this behaviour. As long there's no really working anti-patch out there, we should disable the feature.
Maybe we can set it to 'auto' and enable/disable it only when the User Agent is a MSIE6?
Regards, Garvin.