The replication agent has not logged a progress message in 10 minutes

Hi,

I have the merge replication error message for SQL Server 2008 "The replication agent has not logged a progress message in 10 minutes" pop-up. Also, right-click option for Start and Stop Synchronizing in subscriptions has been disabled.

I changed the heartbeat interval to 20 and this error happened 1 week after I created the merge replication. The merge data cannot sync to subscriber and only solution I can use is drop and re-create the merge replication again but error would be re-occur a week later.

Any other solutions?

Thanks
Teddy