First of, great work on this plugin.. It's nearly perfect!
I found some annoying bug though.. As most other users already stated.. After enabling the plugin and shutting down MSN, the next time MSN is started and the contact list is shown the Error 13 shows up.
It happens on all versions I have tried so far, including the latest which has been released today..
I am not sure where the problem relies, but it only happens when the plugin is set to enabled. Also, when the error message comes up, the plugin sort of "crashes", since after the error it isn't shown at the plugins page either in the configuration settings.
I hope you'll be able to resolve this nasty little bug, since a lot of users can't use the plugin because of it
Good luck!