After re-installing the Google apps package (gapps-jb-20130301-signed.zip) on my CM10.1 phone, Google Play stopped working and didn’t let my install any new apps or update existing ones. To fix the Error[RPC:S-5:AEC-0] you’ll have to:
Go to the system settings -> delete your Google account -> add it again and let your Android sync
Don’t worry, you won’t lose any of your data by doing that.