Alright, there's been several hours since phobos posted. To try and save some time, here's some generic tips to try, phobos.
Restart pc! Yea, seems dumb, i had an issue the other day where i launched mabi, it showed up in task manager for 2 seconds or so, then it killed itself without saying anything. Restarting my pc fixed it. So go ahead and do it just to be safe.
Remove data folders, copies, variants, or w/e all from the mabinogi folder. Don't necessarily delete them, but don't simply rename them either. Pull them out of mabi folder.
Launch mabi at least 3x to see if it works.
That fails, follow the steps for removing abyss in the first post of this thread. Again, don't necessarily have to delete all related files, but you need to ensure abyss is off.
Attempt 3 launches.
If the game works at this point, you need to look for abyss log and share it. If you know what you're looking at, you can quickly fix your problem at this point, if not just remove abyss till someone helps.
If mabi is not working without any mods, make sure your antivirus and firewall aren't causing problems. Make sure drivers and anti-virus are up to date. If you had a windows update, share that info. Windows updates can be screwy sometimes, got one that broke my resolution i was using just this week. The following is not very likely to work, but try disk cleanup, clearing junk files, launching mabi with as few background processes as possible.
I believe logs for normal mabi crashing is in my documents, so you can look for those too.
Make sure to provide as many relevant details as possible when requesting troubleshooting. Wish you luck getting your problem solved, and i would recommend using the tech support section next time.