HP-41CX Halfnut problem cardreader with Nov64d

[Hiwi]

Hi all,
as stated in the subject i have a problem with a Nov64d module and my cardreader:

The Nov64d has Hepax, CCD-OSX and MATH rampages E and F are free. I tried other configs and modules as well.

If I plug in the cardreader and insert a card i always get a checksum error. I cannot read any card.

I tried another cardreader with Firmware 1F but the behaviour is the same. When i unplug the Nov64d module i can read every card!
I seems to me, that the speed changes a bit (quicker).

This is only on a HP-41CX halfnut, but not on a fullnut machine. I have two halfnuts, for both the same situation.

Can anyone explain that or tell me how to fix it?

Ralf