CHarm,
I can't say I have had experience with Keithley's DIO boards, but there is a very similar error in NI-DAQ (NI's DAQ board driver):
"Error -10401
Possible reason(s):
NI-DAQ LV: The specified device is not a National Instruments product, the driver does not support the device (for example, the driver was released before the device was supported), or the device has not been configured using the Measurement & Automation Explorer."
This error happens when you accidentally enter the wrong device number or device handle for the device you wish to address with the driver. For instance, if I had a board with device number 2 and I accidentally identified it as device number 3 in my program, I would get this error (assuming there wasn't another viable resource at device number 3).
In short, I would check to make sure you are identifying the board correctly in the program. If it has a device number or device name, make sure it matches the number or name given to the board by the Keithley driver in the "IO Panel".
<-*DrkOvrlord*->