Good evening from Japan
Thank you for your reply.
Unfortunately, I am not a computer wizard and am almost completely helpless, when it comes to such technical things. I tried the few things I could think of, posted a question on the Ubuntu mailing list (no response) etc., but was not yet able to resolve the issue.
So, for the time being I gave up on Tuxtrans and installed on my second "experimental machine" Ubuntu 10.10.
Now I have two (rather old) computers running Linux: one with 10.04, one with 10.10.
Neither of these versions produces any keyboard related problems on my computers.
I think, this leave only to hope, that some computer wizard knows what to do.