*beats drum some more*
More of the exact same problem here. My server (Ascending Force Siege) is up and sending heartbeats. Yet it simply will not appear on the in-game server list, or in Game Spy Arcade. Only appears if I access through favorites, exactly as others have described above.
There is a shortage of Siege servers!
C'mon Raven/LEC! Provide more support to the admins who run your game at their hardware and bandwidth expense.
Never give in--never, never, never, never, in nothing great or small, large or petty, never give in except to convictions of honour and good sense. Never yield to force; never yield to the apparently overwhelming might of the enemy.
Winston Churchill, 1941.