Groupwise syncing "temporarily suspending delivery"?

Joop,

what does this mean:

2012-06-06 13:15:05.482 DEBUG [ENGINE_WORKER_Thread-4] [filter:213] [userID:cn=xxxxxx,ou=xxxx,ou=xxxx,o=xxxx] [eventID:default.pipeline1.groupwise-source-soapbridge.5604e542afbd11e183360050569103f3] [objectID:default.pipeline1.groupwise-source-soapbridge.7c735814afc011e183360050569103f3] [CheckPoint] Event default.pipeline1.groupwise-source-soapbridge.7c735814afc011e183360050569103f3 is waiting on the add event, temporarily suspending delivery and putting into pending state...

Syncing had suddenly stopped last night with one user reporting that at 0:46 his iphone started complaining it can not connect to sync server. Ok, we fixed that by restarting datasync on the server but then it was discovered that groupwise data wasn't actually syncing anymore and mobility log says that quite a lot.

Now from the message it sounds like some events related to groupwise are suspended for some reason, which might explain why sync is not working. But what might that reason be?

I can't find any actual error messages in datasync/* logs.. I have restarted the POA as well, no change.