Felix used to have one in his D44 and had the same problems with the clicking noise. Froader has since bought his rig and put in a tru-trac now.
I thought i'd try out an Aussie Locker in my D44 which looks much like if not exactly like the other lunchbox lockers. I've been on 2 runs and so for it's been flawless, turning with a locker was a little wierd but it's not as bad as I thought it would be. Best $230 i've ever spent and they claim no tire size limit...we'll see.
Anyways back to the locker issue, I don't know about the other lunchbox lockers but the instructions witht the Aussie locker give you 2 tolerances to check, they say if either of these are not within spec then the case or thrust washers are likely worn and the locker will not funtion properly. I'd check the thrust washers to make sure they aren't warped by visually checking them on a flat surface.
If there are no tolerances given i'd call the mfg. and see if it necessary to be checked and remedied.