System Tasks Negative

Our system tasks on our B2B 4.0.1 server keep going negative and the only resolution is to reboot the server. Has anybody else had this problem? Any fixes?

We have the same problem on B2B 4.6, SP 2. It happens about twice a week.

We have partners sending xml documents to us via a java service that uses TContext.invokeTx(). We are running Trading Networks on our servers. I suspect that one or the other of these is the culprit.