If connected to an SDE enabled Postgres database via ArcGIS (10.1) for a long period of time, maybe an hour +, I will often receive an error from ArcGIS stating "Failure to access the DBMS Server[my schema name.sde.GDB_items]. I can't pin down any specific event causing the error, and my fix is to simply restart ArcGIS. Disconnecting and re-connecting the database connection without an ArcGIS restart results in the same error message.
Its a minor inconvenience, but one that would save myself and others daily grief if corrected. Any ideas?