I'm not trying to be an ass but maybe your band sucks? I know a band like this(except it hasn't hit them yet) who talk about all the BA shows they play(not that you're saying that) and I've been to them and I noticed two things-- 1. They suck 2. There's about Fifteen 5-year olds there. If you're confident it's not your band then maybe you need to just open your range of playing, if you're playing locally and that's all you've been playing keep hammering at that but widen the range of places you play, keep going farther and farther, making a name and fan base for yourselfs. Myspace I don't really think is that great of an advertisement for music, it seems like it only works with established bands and people rely on them after they know them. You need to have a www.com
to show off your band and then once more and more people know you myspace will hit with you guys. Also try to link your band with other bands on your myspace if you're determined to go with the Myspace way--hook up with some other bands you haven't played with before so that fans of that band can see your band. If you're constantly playing with the same band you're just having the same fans. Exchange top friends--you post a band in your top friends and they do the same thing for you so that people that look at that myspace will see your band and check you guys out.
Also be professional--I've ran into a few bands that post those really immature lame posts that say "OMG! Come to our show saturday and we will love you all forever XOXO. I will sell my body to you all if you come." Make it professional--Post the date and time, the place, admission cost, and who's all playing. Don't spam it in myspace bulletins either, I think that's one of the reasons I stopped using myspace is the excessive spamming by bands.