Ouch… this one sounds nasty. Turning “Use Interactive Sequence Caching” off would have been my first choice for sure. I have never experienced this before thankfully, but 2 thoughts that may help:
I have looked into the node, and it sems there are a few cache related options in there. try and set the file. From the docs:
Try turning on a hidden attribute on the file node:
(uca) Use Cache is provided for situations when memory is low. If you turn this on, rendering this file texture will use less memory, but it will also be slower.
Maybe try and setAttr file1.uca 1;
your way to freedom?
Another cache clearing option:
clearCache -all; (goes in to all of the data that can be regenerated if required and removes it from the caches, thus clearing up space in memory.)
For a bit of extra memory:
Consider running Maya from the cmd line. (No UI) That will free up a bit more ram for you.
And failing all of this, you could try and hack it:
Consider writing a mel based expression that
1.creates the file node, assigns the image and connects to the shader/particleShape node
2.runs one frame of the particle simulation
3.deletes the file node
4.flushes the undo cache
5.repeat from step 1 over the course of your animation
Its a hell of a dirty hack, but just may clean maya out enough to work with? Let us know if any of this works, I am sure others will benefit.