Hiyah! I got a weird problem with my particles...
I have 3 emitters and 2 particle types, both are quite heavy and take a while to compute. Once everything is computed and well, they look good... but then I alt+tab, work a bit in Photoshop or whatever, come back in XSI, and there it goes re-computing ALL the particles! Even when I didn't change anything at all, nothing has been modified, it recomputes everything.
The same happens when I do an OpenGL viewport capture... when the capture is over, and it goes back to XSI, it recomputes. It is VERY annoying, because my particles take at least 10 minutes to compute... and even when I press Cancel, I have to mash the button like a madman until it decides to actually cancel the computation.
I have checked all the options, settings... and I have no clue as to what may be causing this. Has anyone experience this as well?
Let me know if any of you got a solution, and thanks for reading this far 
Sincerly,