I'm using a 3204, writing in visual basic .NET on an XP box, and trying to get streaming working. However, after a lot of wrestling with my own program, I tried the one that comes with the drivers and found that it doesn't work there either - I get no results at all out of it.
I've tried Picoscope and it works fine - I assume it works in streaming mode too.
EDIT: I've also just tried the example software in VB6, and it doesn't work there either. The run_streaming function makes the light on the scope turn on, but when it returns "no_of_values" it's always zero.