constant SBBOD with high cpu usage

Hi

since a couple of days ago I constantly get the SBBOD (spinning beach ball of death) on a Mac mini 2011 with Lion 10.7.3.

The system hangs up completely and the only this I can do is click around and move the windows but the clicks don't do anything and at some point after that everything just stops responding.

At this point I'm forced to do a hard reboot (power switch).

After that the system works for a while and then gets the SBBOD again.

During the SBBOD I can see syslog hogging all my cpu usage in activity monitor, but when I try to kill it or click into activity monitor the programm doesn't respond.

I guessed that something else was spaming syslogd with messages but after the hard reboot I don't see anything in console.

Since then I tried almost everything.

- hardware test, the short and long one -> nothing found

- repairing hard drive and permissions -> didn't help

- S.M.A.R.T says verified

- PRAM and NVRAM reset

- logged into guest account and started nothing -> SSBOD after ~hour

- started into save mode and left the comp running -> SSBOD after ~hour

- reformated(not zeroed) and reinstalled Lion(not from a backup) -> SSBOD after ~hour

- ...

Currently I'm trying to disable syslogd to see if some other process hogs all my cpu load instead of it.

I really hope one of you can help me, this thing is driving me nuts :/