|There is no such thing as a keyboard virus as such but there may be one that could do what you see.|
Can I assume that there nothing in common between the systems? You are not using the same keyboard are you?
I can't imagine any defect that would cause both systems to fail this way.
See online antivirus sweeps such as symantec and others.
Not all A/V software can detect every issue. Might have to reload from OEM disks or partitions. Be very careful with usb and other removable media.
Playing to the angels
Les Paul (1915-2009)