Firewire trouble

[paiste artist]

I recently set up my firewire 4/10 and i wanted to lay down some vocals but when i plug my mic into the interface and try to set the i/o channel in pro tools it says output is already in use.

 

[paiste artist]

ok hrmm well if this helps this is what it says when i try to set the i/o

The H/W could not be made active because its output(s) is being used by another active output or insert"