New Pocket Wizards for Nikon cameras, promising HyperSync up to 1/500 and High Speed over radio all the way to 1/8000 have been driving me crazy these days. No high speed at all on the D3x, as it can be seen on this video:
I discussed the issue here with no success,
I also raised a case with PocketWizard, and they have been responsive and fast in replying. At the end, it seems an awkward bug,
"We've just discovered a bug that can cause the issue you've described with a D3x, so I'd like you to take a look at the following settings and confirm if you're seeing the same issue.
First, are you shooting with the D3x set to capture in RAW format?
Second, in the "Camera" icon menu of the Camera's menus, under NEF (RAW) Recording, what is the bit depth set to?
We've found that when the bit-depth is set to 14-bit, it appears to throw off the timings used in High Speed Sync and would cause the exact symptoms that you've described. If you change the setting to 12-bit, everything will work as designed.
Let me know if changing the bit-depth setting gets HSS working properly for you."
14 bit raw is how I shoot, so there it is. I hope that they can fix this with a new firmware release. Kudos to their support staff, not that much to their testing team.