I got this error when starting xend after a filesystem crash:
[2011-12-09 11:05:04 5590] ERROR (SrvDaemon:349) Exception starting xend (not well-formed (invalid token): line 3, column 0)
It sounded like an XML parsing error, but the stack trace in the log didn’t say which file it had loaded. It turns out that it was trying to load something from /var/lib/xend/state/. Purging the /var/lib/xend/state directory fixed the problem, and hopefully had no side-effects.
Thanks to this blog for the solution. I should probably file a bug, shouldn’t I?