Hi,
The event 2101 means that the queue of the health service is full. Try to perform these steps.
1. Clear the cache both on SCE server and SCOM server by running the console from command prompt and with the "/ClearCache" parameter. For example, type "C:\Program Files\System Center Operations Manager 2007\Microsoft.mom.ui.console.exe /ClearCache" and then hit Enter on the SCOM server. The console will open with its cache cleared.
2. Stop the Health Service on the agent, backup and remove the “Health Service State” folder in "C:\Program Files\System Center Operations Manager 2007\" and then restart the agent, so it will send a complete reset of its health service state.
Hope it helps.