Not until firmware v1.55 BETA 5 was Moonshell 2 made the default media player, so the middle Media button won't work w/o a couple adjustments.
On the root of your card create a folder named moonshl and drag the moonshl2.nds file for your moonshl2 in there, then rename it to moonshell.nds.
So on the root of your card you should have 2 folders, moonshl and moonshl2. moonshl will only have the renamed moonshl2.nds file, and the other folder should remain unchanged w/ all of MSHL2's files.
Cyclo looks for the moonshl folder when booting up the Media button, so that's why it's done that way (as DeMoN mentioned).