After two days of testing, I am happy to report that the upstream rc7 version indeed fixes the freezing issue. It still hangs up on suspend/resume, but that's likely unrelated. As I am now using the upstream kernel I'm not sure whether I should report that as ubuntu bug. Any advice would be appreciated. In the mean time I will tag this bug report appropriately.
After two days of testing, I am happy to report that the upstream rc7 version indeed fixes the freezing issue. It still hangs up on suspend/resume, but that's likely unrelated. As I am now using the upstream kernel I'm not sure whether I should report that as ubuntu bug. Any advice would be appreciated. In the mean time I will tag this bug report appropriately.