Through serveral days my friend has done some tests with kernels 2.6.39.x 2.6.39.1, 2.6.39.2 and 2.6.39.3 are still affected. 2.6.39 (debian version 2.6.39-1 from http://snapshot.debian.org/binary/?cat=l) works for several hours without triggering the bug. If it persist for some hours more we will bisect 2.6.39 and 2.6.39.1 and try to find the related patch.