The error message says "the first EverQuest2.exe patched on April 14, 2009" ...or something to that effect.
Again, you should NEVER patch unless it's forced. So -- the only people with troubles are those that did not patch until later in the day. If you patched earlier in the day you should have not patched again until it's 'forced' ...which wouldn't have been this afternoon/evening.
Either way, the proper EverQuest2.exe is always available at isxeq2.twonk.net