USB serial cable issue

[martin at garben.net]

Hi all,
I just bought the RS232 serial cable.
The Reader works fine with reading and writing, but when I plug the serial cable to the reader, my system cannot detect the reader anymore.
E.g.:
OPCD_TEST throws the error in opcd_usb.c right here:
if (ausb_claim_interface(oh->hdl, 0) < 0) {
		fprintf(stderr, "Unable to claim usb interface "
			"1 of device: %s\n", usb_strerror());
		exit(1);

Or mifare-tool shows that no reader is found.
I guess that there is an issue with the USB support and my linux?!

Has anyone encountered such an issue before?

Regards, Martin