@joby_toss - thank you for testing! I'm so glad it worked.
Given the amount of software you test, I don't blame you for turning DEP on globally. "Better safe than sorry" when you're loading new software every day.
Maybe too much information, but if you're curious, here's one possible explanation for why portable software is prone to issues with DEP. Developing portable software involves a number of unique issues. These issues vary from toolkit to toolkit, but one recurring problem I've faced is writing software that works well with multiple versions of Windows.
In the case of my bug, above, the issue occurred in an area of code that deals with enabling features unique to Windows 7. (Specifically, displaying progress bar updates in the taskbar, by coloring the program taskbar button.) In some software toolkits, it's easiest to just compile different .exe files for each version of Windows. At install time, the installer installs the relevant .exe for the detected OS version.
Unfortunately, portable software developers don't have that luxury, because we have to write a single .exe that covers many different Windows versions. In the case of my bug, I was dynamically creating a chunk of Windows 7 taskbar interface code at run-time, if Windows 7 (or later) was detected. Unfortunately, this involves loading and unloading the taskbar interface in a non-standard way, which triggers DEP crashes. (DEP works by restricting where programs are allowed to execute code. A common trait of viruses and malware is running code outside the normal application memory region, which is exactly what I was doing to enable Windows 7 behavior conditionally. Why not use a normal taskbar interface in PhotoDemon? Doing so would cause crashes on Vista or XP installs, argh!)
Programs with normal installers don't have to "jump through hoops" like this. I envy those developers.
Anyway, this is probably irrelevant information for non-coders, but maybe interesting if you run into StackHash/DEP crashes in the future. Thanks again for helping me with my bug.