[tor-relays] torrc "permission denied" warning

In the Tor logs for a relay, I get the following message:

Dec 19 19:42:23.662 [notice] Renaming old configuration file to "/etc/tor/torrc.orig.1" Dec 19 19:42:23.662 [warn] Couldn't rename configuration file "/etc/tor/torrc" to "/etc/tor/torrc.orig.1": Permission denied

I've played around with file permissions but it doesn't help.

Tor seems to be working. Does the error matter?

Running Tor on a Ubuntu Server 10.04 LTS

Feedback much appreciated.