If I use
!Mute [0]

it says "Exception during bang command execution. Please contact the module author. Bang parameters: [0]"

If I try
!Mute 0

...then I don't get the error message, but nothing else happens either..

I can try muting any number and nothing happens.

psynapse, do you use win2k? I've suspicions the mute bang modules only work with 9x systems..