Bukkit

What steps will reproduce the problem?
1. Start an arena with 3 players
2. Have 1 of them leave the server and join again on a separate world.
3. Guns cant fire for other 2 players, and errors in console

What version of the product are you using?
Quake Version 2.4.1

Do you have an error log of what happened?
http://pastebin.com/Dj8iJajF

Please provide any additional information below.
If I can access the source (GitHub), I might be able to solve the problem.

Suggested fix: Every now and then, check to make sure all of the players listed in the arena are online. If not, remove them from the arena and add them to a separate list. When they rejoin, clear their inventory and effects (This also fixes the bug with the items and effects staying after rejoin.)