This Bug is nov SOLVED!
In the changelog of the new prerelease 185.18.14, the NVIDIA team says:
"Fixed a Xinerama drawable resource management problem that can cause GLXBadDrawable errors in certain cases, such as when Wine applications are run."
In addition, I did a quick test myself and can confirm that it seems to be solved (I'll some more tests soon, but I expect the problem to be completely solved now).
Thanks to everyone who helped us gathering all information and thanks to the NVIDIA team for solving this bug