Ok, now that I'm using a portable version of Gimp 2.8.1 64bit I was able to get Mathmap to work. However, when I go to Gimp's Filters/Generic/Mathmap drop-down menu I don't get the list of Mathmap filters like I used to; I only get the option for opening Mathmap, and when I do there are no filters listed under the filter heading. Anyone have any suggestions as to what I'm doing wrong? I feel like such an idiot with these sorts of things.

Charlie, are you talking about the extras folder? If so you have to download that separately.
Extra Folder

Molly,
Thanks for trying to help. I somehow figured out what I was doing wrong. With Partha's 64bit Portable you have to put the Mathmap folder (the one with the Expressions in it) in the pref1 section of the main Gimp directory. I did that and then was able to view the filters, etc.

Here's a flower, just for you for helping out.

Awe thanks, that is beautiful. Glad you are up and running