---- SOLVED ----
Well, this isn't the first time I've found an answer to my own problem after posting, but hopefully this will help someone else out.
I output the $_REQUEST array at the very beginning of my module run to see what was being generated from the module that might be messing up my $_POST values, by running:
print '<pre>';
print_r($_REQUEST);
print '</pre>';
nothing fishy going on with what I saw come out the other end... but I left that code outputting values as I ran different methods in my module. What I found was that $_REQUEST held onto my HTML tags from my form submission, but $_POST didn't, so when I did my SQL INSERT statement I had to call my posted form variables by $_REQUEST['variable-name'].
For those who may not know, $_REQUEST hold the values of $_POST
and $_GET (which can be handy when passing variables around between pages sometimes).
I have no idea why $_REQUEST and $_POST have different values when the form method="post".
Hope this helps someone, and if anyone knows why this might be happening, I'd love to know.
T.