sorry, which PM button are you talking about?!
a) the envelope button shown with each musician in the jam view?
b) the envelope button on the profile pages?
c) the blue-envelope button above the shoutbox?
d) the grey PM button below each forum post?

sorry to be picky, but this info will save me at least 15minutes :) please let me know the browser you use, too. And of course: thanks for reporting in!