Ok, so for some reason when I restarted my computer, the problem went away.
I did install Internet Explorer 7 Beta 3 right before I installed msgPlus Live, and IE said (after installation) "You will need to restart your computer, or some programs may not function correctly". But instead of restarting I pressed "Restart Later". So perhaps thats why msgPlus Live didn't work until after I restarted?
Anyway, it works now