Thanks all for your kind input, we have installed CDS13 and now the problems are solved. I would like to thank all of you agian to point us into the right direction.
Currently no patches applied, we where looking onto the site of IBM and found out that there is a patch 6 where a problem is fixed that might be related to ours?
Im not sure if this is the correct place to post this issue but anyway ...
Some background :
We're implementing an application that is using MQ client to connect to a remote queue manage ...