Didnt find a bug report or known issue on that (tho i might be blind). When directly rendering FumeFX enabling motionblur
hangs on “Retrieving Particles” forever.
That’s on Windows XPPro x64, Max 2k9 sp1 x64
Regards,
Thorsten
Turning on Motion Blur will cause Krakatoa to get the Velocity channel from the Fume sim. Is there anything funky about your Fume velocity channel? I’ve heard that Fume doesn’t handle velocities very well, are you sure that it isn’t just thrashing around in the page file because you spilled out of main memory? You can check using Process Explorer or Task Manager to see what kind of memory usage is reported for Max when these hangs are occurring.
Let me know what you find out.
Been taking a closer look at what happens without any real result tho 
The ram usage (both real and virtual) stays exactly the same down to the kbyte when hitting render and it initially stalls with 0 cpu usage.
Ram usage is at 450mb (it’s a not too complex setup and simed at rather moderate detail. the same i posted to the “Testing Direct Fume Rendering Thread”)
This is a 12Gig Core i7 maschine so Memory doesnt seem to be the problem.
I displayed the velocities in the fume container and they seemed fine visually (no overly crazy spikes or anything).
Is there a way to take a closer look at what is actually in the velocity chan ?
Regards,
Thorsten
Okay…stupid me 
It works if the operator is mentally capable to read the docs and add a Krakatoa Fume modifier to the fume container to enable fetching of the velocity channel as otherwise :
Would be nice if it would catch it, pop a warning and ignore the moblur.
Regards,
Thorsten