[raymo]

I appreciate your help. I have tried on my desktop as well as my laptop.
I bought the mount used a year ago, and it has always worked fine.
The cable I am using is new, as I didn't get one with the mount. It is actually two cables; a short one with a DB9 female on one end and USB at the other.
The other cable has the DB9 male on one end and the RJ11 plug on the other. Both supplied by my local Skywatcher dealer. He uses this set up
himself. He knows of one guy that had the same problem a while back, but unfortunately doesn't know if he overcame the problem. It is a bit
baffling because as I said, the laptop dings when I insert the USB plug,
which would suggest that there is a complete circuit through the cable.
If the cable was open circuited the PC wouldn't know it was plugged in.
Incidentally, you're up late.
raymo
P.S. I tried all 4 USB ports