Progressive slowdown

I posted about this in bugs, but I am convinced I must be doing something wrong.

I am repeatedly running one image over and over as I am optimizing my pipeline. At first the program runs quickly, but it gets slower and slower until it finally stops responding and crashes. I am running Windows 7 on a computer with 16 gb of RAM and it seems like I am running out of memory. I have talked to some people who know computers far better than I, and they suggested that each time I run the pipeline the memory is not clearing. I have no idea how to fix this beyond just restarting the program every few runs.

Any advice on how to fix this would be greatly appreciated.

Hi Rachel,

Please see my response over here.
-Mark