As the title suggests, I can't get JJ2 to start. Have DEP disabled for everything except Windows programs, and run in administrator mode. I also tried the JJ2+ beta, which doesn't help either.

Running Windows 7 64 bit if that helps any. Tried Antivirus on and off with no difference.

Try to open Jazz2.exe into game folder

Tried that as well, no luck. The error is an Access violation window.

Some games required Directplay, and latest redist of directx (june 2010) need to be installed

I tried the DX redistributables, which didn't work either. Here's the error window.

Try reinstalling the game, you might have a corrupted download.

That does narrow down the search a little, but unfortunately this time it's not enough to determine the exact cause. There are several things you can try.

First off, you can send us jazz2.log from your JJ2 directory. It contains some diagnostic information in human-readable format that may help us determine more or less at which point the game crashes. Side note: the file contains data such as file path and host name, so if you consider some of that to be sensitive information (e.g. it contains your full name), you may want to edit it before sending it.

Second, you may try running JJ2 with different arguments. You may find the list of supported arguments and how to use them at here. Arguments especially worth trying are: -safe, -nosound, -notriple, -menu. You may also try using a level filename as an argument, such as bbswing.j2l, as this will skip any intros and menus and run that level (does not work for levels that are part of the official campaign, hence why I recommend bbswing.j2l, a user-created level distributed with the game).

Using -safe helps me get to the Epic logo. However, once the logo finishes, the game crashes. I don't think jazz.log is going to be informative, as it is empty except for information on my system components.

If you only recently disabled DEP, have you rebooted your computer since disabling it?
Just wanna help rule out every possibility, juuust in case. I nearly forgot to do so myself when I disabled DEP.

Yes I have.

Going to try the game on my work computer once the weekend is over. Not sure if it's limited to my home computer.

I'm having the same problem, base game crashes instantly (jj2+ version works fine tho!)
what I have found is that running the game with -nosound makes it run perfectly, except without any sound (-safe still makes it crash for some reason even though that should disable sound as well) works with both DEP on and off.
I don't own any original JJ2 releases so I can't verify but jazz2.log when running without any flags mentions this:
SND: Galaxy Music System v5.0a
SND: Detected DirectSound driver

Now I don't know if "Galaxy music system" is a part of GOG galaxy or it was actually a thing in the official releases.
if it's a gog specific hack then it may be what's causing crashes when there is sound enabled.

Galaxy is in fact a very old sound library originally used by JJ2. We know what causes your crash: it's a data race involving said music system (a type of multithreading error, hard to debug). To my knowledge it occurs rarely on Windows and far more often when using Wine.

We indeed patched this problem in JJ2+. Without JJ2+, the only solution to avoid it is to run the game without music. I got such a request before, so if there is sufficient demand, I might look for a way to release a stand-alone fix to this crash that doesn't require running the rest of JJ2+. Although, personally, I don't see many valid reasons not to use JJ2+, especially since that's far from being the only crash we fixed.

Well I have no issues with playing the game with JJ2+, just thought I'd mention what i've noticed.
Tho its a pita to set up with GOG galaxy since you have to disable automatic updating of the game then install the standalone gog installer for JJ2+ on top if you want all the episodes to appear in game.
It'd be better if the optional JJ2+ installer included all the game files so you could just install it through the beta branch in galaxy.

Thanks for clearing up what the "Galaxy music system" is :)

EDIT: messed up my quoting

This might actually be useful information. I just tried running the game with -safe myself, and oddly enough it also crashes after the Epic logo. The Epic logo is normally followed by a 3D animation of an Orange Games logo, which unlike all the other animations is not pre-rendered and that may be causing issues in safe mode. I find that the game is still possible to run with -safe if intro screens are skipped so that may work for you. Confirm that your JJ2 directory contains bbswing.j2l and try running the game with the following command line:

Jazz2.exe -safe bbswing.j2l

Also, so far most of the information you provided matches the error mmodri mentioned, however this error shouldn't occur in JJ2+. It is possible that your JJ2+ installation wasn't correct for some reason. In particular, to the best of my knowledge based on user reports, if you install JJ2+ using the provided installer, but your GOG Galaxy branch remains set to JJ2 TSF without JJ2+, and auto-updates are enabled, GOG Galaxy will notice that some files differ and "update" them, thus erasing efforts of the JJ2+ installer. Just to make sure, you can verify when you're running JJ2+ by reading jazz2.log afterwards; the second line should be as follows:

LOG: Jazz Jackrabbit 2 version JJ2+ Beta v5.5 (2017-06-01)