Unable to use Alt-Gr

Hi everyone,

I'm running my Workstation on Windows 7 and CentOS 6.2 as guest system. I'm using the guest system for development and often need combinations like Alt-Gr + 7 or Alt-Gr + 0. But I'm unable to enter any chars using Alt-Gr... is there any (known) bug or any option I've to activate to use Alt-Gr in my guest system?

Thanks in advance!

Edit:\\ I'm sorry, I posted the thread in the wrong section... can any moderator move the thread to Linux Guest-Forum?