I ran some further tests (on a fresh 10.04 installation) and it seems the problem has been introduced with the 2.6.35 kernel.
Using different vanilla kernel the problem started to appear with the 2.6.35 line. 2.6.34.10 was still doing fine.
I weren't able to look at the changes between .34 and .35, but maybe some is willing to take this as a starting point.
I ran some further tests (on a fresh 10.04 installation) and it seems the problem has been introduced with the 2.6.35 kernel.
Using different vanilla kernel the problem started to appear with the 2.6.35 line.
2.6.34.10 was still doing fine.
I weren't able to look at the changes between .34 and .35, but maybe some is willing to take this as a starting point.