I'm running 6.10.5 on both viewer and host. The host itself can receive letters, both capital and not, but I'm running a virtual machine on the host and that won't accept capitals. It's only capitals too, lower case are all fine but if I hold shift or put capslock on then no input is received.
I recommend that you check your virtual machine software settings, specifically those that govern how keyboard presses are sent from host (virtual machine host) to guest.
