Finally I figured out why my favorite synchronizing software didn't work in a few months. I spent countless hours reinstalling it and java (DirSyncPro is java based) and scanning the PC for viruses and malvare (none found with numerous different products).
Last night I started going through my services and starups and tried to disable everything non-Microsoft (in steps to pin point an offender). I actually got error messages in msconfig that I don't have clearance to change things even though I'm administrator on my XP SP3 PC. The errors coincided with the ForceField.exe and IswSvc and that made me suspicious.
I googled for those and turned out to be Force Field by Checkpoint.
Weird, since I did not buy this or signed for evaluation etc. Zone Alarm Free apparently installed it for me during update even though I always opt out from toolbars and other fluff.
I'm posting this in case someone comes across a similar problem, as this is not documented anywhere (that I could find at least).