I check the logs again and I found in the last days several entries like this:
2010-09-12 19:29:29 2010-09-13 12:11:42 2 302 Warning WorkingSet: Virtual Memory is growing beyond parameters - 23.797(22.393) GB
and a couple of entries like this:
2010-09-12 19:29:29 2010-09-13 12:16:22 1 120 Error Server aborted trying to recover by restart. Reason for restart: Internal inconsistency, type D, detected.
I talked to Qlikview support and told me that there are stability issues with SR5, that next 22 they will be releasing the SR6. I hope that SR6 includes fixes for this issues.