I have asked this question in the old Kyma Forum but after some modification of my setup the problem is still present.
I followed all Doug's advices. Furthermore I changed the cable and TC konnekt 24D so far - but without any improvement. During computation of my multigrid paca is freezing and I get the error message " The Paca is not responding. Unhandled FireWire bus reset or FireWire error. (22)" .