Magic Mouse not discoverable - Help

[Soogs]

Hey all, got a second hand MM and i cant find a way to pair with either of my macs

mac mini 2,1 running 10.6.8
imac 5,1 running 10.7.(latest)

the power led comes on for about 3-4 seconds and then double blinks so it looks like everything is going fine but the macs cant see it.

ive tried turning bluetooth off and on. turn off bluetooth and restarted (and shut down, reboot)

ive tried erm doing that thing where you shut down and hold cmd,opt,p & r

also tried deleting the com.apple.bluetooth.x.x files as suggested on many pages and still nothing.

have i been sold a dud mouse?

is there anything else i can try before getting the hammer out?

thanks in advance

 

[shine]

Have you tried changing the batteries?

 

[Soogs]

yeah i should have mentioned that

ive tried 2 sets of duracell and 2 sets of jcb and 2 sets of ikea brand batteries... all fresh from the pack with good expiration dates

also tried the rechargables i use in my old wireless mouse and kb