I'm guessing that you must have a compatibility issue with other software or a bad copy. I also have a Cobra and SDM 1.4 and the incredibly expensive cable.
I use SDM with W2Kpro and Win 98 and never had a crash.
Have you tried reinstalling a new version?
I have a friend who could not get SDM to work with his WinXP, Finally he downloaded the most recent version from Suunto and that cleared up the problem. By the way, he had to totally erase the old version first. Installing the new version over the old one did not help.
Downloading from the computer to the PC is another thing altogether. The interface is very finicky. I had a heck of a time getting the two to talk at first, then it just started to work. I don't think I did anything differently. It worked flawlessly after that for over a year, 100+ downloads, then it stopped again about 2 months ago. A bit of swearing cleared up the problem and it works again.
It seems to be related to the phases of the moon. Or not.
Gerry