I got this installed on my synology nas, ill check that what ever it uses to unrar is up-to-date. i presumed it was part of sabnzb. Thanks for the help
edit. yes it says "Enable built-in unrar functionality."
This has recently started happening to me files have problems repairing or extracting however i use the same files on my mac usenet program and it works straight away. its almost happening on every nzb now.
I have turned off enable_recursive it doesnt seem to get new nzbs anyway