update dss5 to dss6 - scst issue

hi,
yesterday i updatet one of our dss5 boxes to dss6.
with ietd enable anything works as on dss5.
i wonder that there is no better performance with dss6...

when i change to scst our xen server cannot connect to dss6.
xen server does not find any targets and luns.

i recreatet the targets and volumes with no effect.

i wonder if there is anyone outhere who managed xen and scst.

we use citrix xen 5.0 enterprise.

greetings
roger

update:

for iscsi target i use these settings:

MaxRecvDataSegmentLength 262144
MaxBurstLength 16776192
MaxXmitDataSegmentLength 262144
firstBurstLength 65536
DataDigest None
MaxOutstandingR2T 8
InitialR2T No
ImmediateData yes
HeaderDigest None
Wthreads 8

after i change MaxXmitDataSegmentLength to default 262144 i can acces the targets from xen (using scst)

any suggestions?