EPM2007 - importing actuals using PSI

We created custom code using the PSI for importing actuals into EPM2007 from another system. We are using impersonation in the interface code for the Statusmanager and every Status Manager has a rule for automatically approving all Task Updates. This is working fine except for the situation where task updates are applied while the project is checked out. The queue shows the TaskUpdatestatus job with status 'skipped for optimization' and reaches no more than 20% and is never finished.  Actual hours do not appear in MS Project.

Any suggestions are welcome,

Marcel Visscher