@oukej - is this a dead issue, or something that is still being considered for inclusion? (Or maybe you're about to mark this closed because it's coming out in the next update? ;) )

Happening with multiple modules and triggers... lots of displays. Two workarounds that have worked for me, as suggested by others: Drag the interface out of the middle of the screen, and it'll work; or change your display size away from Small (Very Small and Normal both worked for me).

This also happens with CUP Harrier

We were getting the same thing. There was a patch released Thursday that addressed it. Ran steamcmd to update the server (had to run it a couple of times - running it once didn't resolve the problem, running it a second time said that the server was already up to date but it did remove a couple of queued files). After making sure server was up to date and that Steam had downloaded the update to the game, the original password worked again.

EXE version 1.42.130.340

http://dev.arma3.com/post/spotrep-00041