I know some other people were having issues with The Arena (specifically those who downloaded a client install other than Titanium for 2.5), here is a fix:
Remove the following files from your client directory:
arena.eqg
arena_EnvironmentEmitters.txt
arena.zon
Generally "old" zone files from titanium work better.
Just another chore put on the players,replacing the zone files for 178 zones is almost as much fun as distributing AAs again or rebuilding the UIs/macros for all your chars.