I have a very similar problem on Windows XP. I install the software (included on the CD) for the PicoScope3204, I connect the device, it is detected as PicoScope without a problem. However, the moment I start the Picoscope6 software, the device seems to turn off (the red LED turns off, and I can hear the faint clicking sound of a relay switching).
The Picoscope6 software than does not detect it.
I tried in on another PC with Windows XP, and it has the same problem.
What is interesting, that this same device works without problems on a Windows 7 machine.
I really need it on my Windows XP workstation, is there a solution for this? The documentation says that Windows XP is supported.