for further tracking and bisection, the problem was still present after an upgrade to precise with a 3.2.0-23-generic kernel. using v3.4-rc6-precise (3.4.0-030400rc6-generic_3.4.0-030400rc6.201205061835) again seems to fix it.
for further tracking and bisection, the problem was still present after an upgrade to precise with a 3.2.0-23-generic kernel. using v3.4-rc6-precise (3.4.0- 030400rc6- generic_ 3.4.0-030400rc6 .201205061835) again seems to fix it.