Can't hear anyone on mumble

[DoubleCore]

Ok I have this problem for a really long time and it really getting on my nerves!
Project reality works fine but PR Mumble doing some problems.
As the title says - I can't hear people in-game.

I tried to re-install Mumble - don't work.
I tried to re-install PR - don't work.
I tried to re-install BF2 + PR + PR Mumble - still don't work.

I've created a new soldier and it still DON'T WORK!!!

Every time I enter my Player Name in the MsgBox, I get this pop-up:
http://i.imgur.com/mYrK2.png

Any ideas?

[Mineral]

you once registered a name on your computer. Now you can't use another nickname but that one
OR
you registered that nickname(or somebody else) on a different computer so now you are unable to use this nickname.

[LITOralis.nMd]

Simply change your Nickname for the PRMumble server to DoubleCore_ or DoubleScore2 or something like that.