Lower-case Letters Not Working to Label Machines

Something of a strange problem - more annoying than anything.

When trying to label a newly-added client to the machine inventory, I cannot seem to use certain lower-case letters on my keyboard, specifically a, z, x, and c. Put simply, nothing happens when I press these keys (though the other letters work just fine). However using capital letters (A, Z, X, C) works without problem.

Server login is through Windows Remote Desktop. I have confirmed this occurs whether logged into the server from my desktop or laptop, so definitely not a problem with my keyboard itself.

Has anyone else encountered this?

-Rob