Just wondering if anyone can offer advice, regarding a problem with particles seemingly changing velocity in the middle of an animation. (Thanks in advance for reading this long post).
Animation details:
The animation is 378 frames long.
There are three particle emitters.
All emitters start prior to frame zero, and end at frame 378.
Particle life for one emitter is 38. The other 2 emitters have lives set at 4000.
The “Anim” panel in the Render buttons is set to render frames 1 thru 378.
The problem: At frame 250, all existing particles, for all three emitters, suddenly freeze, and new particles created in frames 250 through 378 don’t move at all. It’s as if the emitters’ velocities are suddenly changed to zero. My intention is that velocity is constant throughout the animation.
(All emitters behave as expected in frames 1 thru 249).
One emitter was set up for a velocity of 4, and the other emitters have a velocity of 0.3.
I wouldn’t even know how to change the velocity on purpose (in the middle of an animation), if I wanted to. But effectively it seems that’s what’s happening. I don’t have an IPO curve for the velocities, so I don’t know how to observe any unexpected changes in velocities (outside of viewing the animation).
There are no force fields or deflectors acting on these emitters. There are some force fields and deflectors acting on OTHER emitters, however, all of which reside on other layers. I’ve checked to make sure the force fields are not accidentally changing layers within the animation, and I find no problems there.
Nto sure why this is happening, and why the problem occurs on all three emitters at frame 250.
Any ideas on what to check for, is much appreciated! 
Thanks.