Avast 4.8 Home On-Access Issue

Anyone have the On Access Protection quit on them? I’m getting a message that the AAVM subsystem detected a RCP error. Nothing has changed with this system - running in a Vista environment and, until yesterday, running smoothly. Any ideas here?

Have (or did) you another AV installed in this system, if so what was it and how did you get rid of it ?

When do you get this error ?