Exchange RPC Client Access service starts then stops after SP3 ungrade on SBS2011

I have upgraded my SBS2011 running Exchnage 2010 to SP3.

All the users poutlooks now cannot connect to the Exchange. I believe it is because the Exchange RPC Client Access service starts then stops after SP3 ungrade. They can use OWA to view their mail and mail is being received and sent as normal.

I am at a loss of how to fix this and cannot find any answers on the web.

I am thinking of just restoring it back to the day before but need to either:

1) Find a solution and fix this

2) Restore the server to the night befores backup - on this I have a question as don't know after SP3 if I need to restore the AD and system state and then the Exchange and Sharepoint Application or just the Exchange application. I know SP3 makes Schema changes so am unsure as to how to restore this server and not loose any mail that has come in the past day.

Thanks,

David