http://bugs.winehq.org/show_bug.cgi?id=28044
--- Comment #7 from Emanuele emanuele.emalele@gmail.com 2011-08-10 13:29:41 CDT --- Ok the problem is clear.
After your post I checked up the 32bit Mesa and... they are of January (!!!).
You're right about corruption: also with my forcing the graphic doesn't appear clearly.
By googling I've found that it's a Gentoo known problem and the solution is to build up a 32bit chroot environment into the 64bit one.
I'll post a new reply just to confirm that the Gentoo suggested workaround has... worked :)
Thanks for your support.