Causes Of Out Of Stack Space Error "28"

i was hoping to get advice from anyone familiar with the "out of stack space" error. basically i'm building a UserForm-based app which reads spreadsheet data and stores it as a module-level variables (well, an array). the different buttons lets you edit the variable, and once you're done it writes back to the spreadsheet.

at least, that's the idea - lately i've been running into a lot of "out of stack space" errors, which have been pretty hard to pick out because my app's grown to the size where it's not so easy to pick out the root of the problem. what happens is the app will let you perform operations on the data with no error, but after repeating the operations too many times the application tells me i'm out of stack space. i've read up a bit on the error, and here's the list of possible causes i'm using as reference: Out of stack space (Error 28)............