Am I nuts or my Drebel can x sync at 1/320?

[DocFrankenstein]

I am confused.

When I was viewed this shot, I was dissapointed:
http://photo.klein-jensen.dk/public/Dia_Hair_Web.jpg (66kb file)

There's motion blur in it, at 1/125 sec. For some reason I remembered reading that rebel will sync at 200 with EX flashes and 125 with non EX.

So naturally, I kept Av=10 and Tv=125

But 5 minutes ago, I took out the Drebel and took a shot at 200... the frame was white... I took a shot at 250... 100% white... 320... 100% white...

Only at 400 did I get the bottom of the picture to be unexposed to the flash.

And I am using 1/16th (lowest power) on my vivitar. So that should give a burst of light which lasts 1/10000th of a sec or something like that.

I am sober BTW. But can't find my rebel manual.

How is this possible?