kishy, i had the phenomenon that one of my keyboards were missing some keystrokes when using the "AT to PS/2 adapter". I connected an alternative adapter (same model but only bought it recently) and it worked fine mostly. I can only imagine that the old connector has had some kind of defect, what do you think?
ripster, you are a mysterious guy, I always only understand half of what you want to tell me

When I see that correctly this blue cube is for PS/2 connections only. Im not sure how that can help me in this case. Do you mean that an additional connection via USB will improve the situation?