I have done tons of fiddling around with this (reinstalled CLEO and DYOM, downgraded to CLEO 3, etc) to make sure it's not something stupid but I have come to one final conclusion.
Basically, when I try to load DYOM, it crashes. As you can tell, I do have CLEO 3 installed, and last time I installed this mod a year or so ago it worked, so I shouldn't have any problems with wrong version or anything, because it's remained the same ever since. Anyway, what I've discovered is that if the cleo.asi file is in the GTA SA folder, everything crashes. The loading bar gets about 5/6 or so of the way through and then crashes, whether I'm loading or starting a normal game or attempting to load DYOM. However, if I take that file out, normal games work as they should, but naturally, DYOM crashes AFTER the loading finishes and fades to black. So I'm left with a bit of a dilemma. If I leave the file in, everything crashes, but I can't take it out because it's needed for the mod to work, so I have no idea what to do. Of course, I might just be looking at everything wrong and it's something else entirely, but I honestly have no idea at this point. Coming here and leaving a post is my last resort, because I don't know what else could possibly be done. Also, apologies if this is in the wrong place or something, but I haven't been in this section for years.