Sorry for the lack of proper nvidia-bug-report.log file. I'll send it tonight.
In the meantime, i can give you the first "bad" commit ID :
[ec97383f6fb1a14c19dfcb85dd5239a8938c9e3c] wined3d: Add support for ARB_framebuffer_object.
The second one also adversely impacts the frame rate, but not as strongly :
[34dd27e3a8f9affb919db6f7c912040ded8eace8] wined3d: Don't create a depthstencil renderbuffer if ARB_framebuffer_object is supported.
This "bug" is reported in Wine bugzilla : http://bugs.winehq.org/show_bug.cgi?id=20307
Within is mentioned the quick fix Henri Verbeet suggested to work around the issue.
Thank for your quick reply!