Hey, Flatty!
ok... find the metronome buss (on the rt, near/in the same group as the Master buss...) if you don't see it, press H which will bring up a track list you can click to hide/show tracks... make sure it's checked... save.
Now look at how the metronome buss is routed... if you can't see (console), go up to the top left (Modules) and make sure in/out is checked... now look at the bottom...the metronome track is probably routed to the Master or some buss going to the Master... change this so the Metronome is going directly to your soundcard, in your case your Presonus firebird thingy...
Also make sure some effect like a reverb didn't get put on the Metronome buss/track by mistake...
That should take care of it...
You should make sure your "normal" start setup is this way or you'll have to do it every time... also, any song templates. If you built them with the wrong routing, they all need to be resaved after fixing them.