Currently available MegaGlest gameservers are listed on Play.MG.
some ATI drivers have weird OpenGL bugs.
The game is very slow in Debug mode, specially with a lot of particles on it and an old computer. Try using auto inline and disabling assertions.
Try running the game in a lower resolution. i find that helps with most graphics problems. or, put shadows on 'projected'
if it is still slow...then turn your music off...