When i try to access the on-access scanner ( i’m using version 4.1 home version) I get the message Subsystem detected a RPC error, the operation could not be completed. I’m using windows XP Pro. ???
sorry, that should read AAVM subsystem detected a RPC error, the operation could not be completed.
Can’t remember I saw your name earlier here. Eelcome to this board!
Already remove Avast, rebooted, reinstalled?
Also use the search function here and use the keywords “aavm” and “rpc”. A lot of threads here are already dealing with it and have possible causes/solutions.
Good luck.
;D reinstalled the software, everything works ok! A bit scary, seeing that i installed the software only yesterday!! Lets hope this is just a blip!! ;D
Nice too see it is solved. Spend some time reading the manual to discover what settings you can change and what they do. And if there ever is another problem… You know where to find us 
And for questions, problems and other things not related to Avast, you can always use the off-topic forum here. 
You followed the most common solution for RPC error.
Do you have (or had in the past) any other antivirus installed in your computer?
Do you use a firewall? Which one?