It's too bad most instruments sound like crap through MIDI.  *sigh*  No musicality at all unless you buy $400 composition software.

You should experiment some more with chord structure and progressions.  A melody is fine and dandy, but harmony and counterpoint are what makes it go somewhere.

Must...not...start...babbling...music...theory... x.x

Try experimenting first, before you come up with the melody.  After you have some chords laid out, just hum along with them and let the melody form on its own from the chords.  Then there won't be any 'wrong' notes. :)

It doesn't have to be complex.  Just some basic 3-note triads that rise and fall with the melody would be great.  Or forget harmony all together.  Write a countermelody that moves when the melody isn't doing much and vice-versa. </band geek>