I have an Exchange 2003 SP2 installation, FS1. A second Exchange 2003 SP2 was installed in the same organization, FS2, to migrate everything from FS1. Folders replication was configured and all mailboxes were moved from FS1 to FS2. Public folders failed to replicate despite much troubleshooting, so for the time being it was decided to back out and move everything back to FS1.
Then I moved all mailboxes back to FS1, but the error continued. I ran ISINTEG once again on both priv and pub stores of FS1, again no change. This event is strangely popping up every 12 minutes, then again after 3 minutes, then back to 12 again and repeats with this 12-3-12-3 cycle.
I also found http://support.microsoft.com/kb/828875 which suggests this issue occuring with exmerge and links to a hotfix, however the hotfix is for Exchange 2003 SP1 and I'm concerned with using it here.