Matlabpool set() invalid handle error

I am using a genetic algorithm to optimize a (proprietary, sorry) problem that takes several days to compute. To monitor progress (aside from the built in plot functions) I have my fitness function plot results every few iterations rather than once a generation. To do this I pass a pre-defined handle to my fitness function and use set() to identify the current figure without bringing it to the foreground.

This works fine under normal circumstances, but if I open a matlabpool I inevitably get an error in set() saying that the handle I have passed to the function is invalid. If I create a new handle each time with figure() it is not a problem. This pool is entirely local. I am only using it to run parallel threads on separate cores, which happens to be faster than a single thread sharing resources.

Are there additional considerations I should make when handling figures in a computing pool?

I have had this problem in both Matlab r2012b and Matlab r2012a