Thanks for your last comment.

You recommended to re-install the USB interface drivers. However, I do not know how to do this on a Mac. I never intentionally installed any driver for using the...

We use Parallels on some of the Macs, but only occasionally.
The problems described were all encountered when working on Mac OS (our experimental software is Mac-based).

Just for trouble-shooting...

I don't know - sorry. We no longer use any versions other than 10.5 and 10.6.

In 2008, we ordered DirectIN Precision Button-Boxes (High-Speed USB Response Boxes).
Some of the response boxes are used with Windows (on a PC), some of them with Mac OS X (either with 10.5 or with...