on my Windows laptop the volume control keys (Function-F8 and
Function-F9) get intercepted by mrxvt have the equivalent of typing
characters "b" and "c". Oddly enough, other control keys (e.g. for
brightness) don't get caught by mrxvt. It gets annoying sometimes,
but I don't know how I would start troubleshooting... Let me know if
you've got any hints!