Ok
For starters once Dragon starts compiling your map is toast. So if it craps out in the middle with a fatal error then you are going to get a map with a filesize different than 75,264kb. Map0.mul=Map0.mul=Map0.mul. No matter what you have in it, it is always going to be 75,264kb. Not a kb more, not a kb less (this is of course for a proper working map).
Anageth, there are a multitude of reasons you could be getting that error. If I were you I would erase my dragon folder (after moving my bmp and any custom scripts out of course). Then reinstall dragon.
Now when you go to setup file paths (and this is good advice for the rest of you) make a new directory outside of the dragon folder and copy muls there. Also you should go into your UO folder before you do anything and copy all your muls into a backup folder. If you already screwed your UO up you should reinstall it, repatch it, then backup the muls. I cannot count how many times that has saved me from having to reinstall UO.
I'll share my folder paths for anyone still reading along. I have the luxury of having 2 servers and numerous workstatations in my house which most of you may not but my setup is still easily adaptable for a single computer.
My workstation-
D:\ - My data partition.
D:\UO\ -UO 2d Client.
D:\UO\Mulsbak - Backups of OSI mul files.
D:\UO3D\ -UO 3d Client.
D:\UO3D\ -Backups of OSI mul files.
D:\UOTools\ -All my UO related crap goes here.
D:\UOTools\Dragon\ -Dragon program files.
D:\UOTools\Maps\ -All my bitmaps for Dragon and other map related art.
D:\UOTools\Work\ -This is my output directory for Dragon as well as my working directory for WorldForge.
My server-
F:\ -General applications share on my servers data partition; if I were to run a live server, I would change this for security reasons to be in it's own share.
F:\RunUO -My RunUo server install.
F:\UOData -The mul files that the server runs off of.
Process goes something like:
I edit images from D:\UOTools\Maps in Adobe Photoshop
Run Dragon and DragonSP, Output goes to D:\UOTools\Work
Run Worldforge to tweak
Copy muls to whichever client I am using and F:\UOData
Run around and inspect the map
Copy muls to D:\UOTools\Maps\Mapname\ if I am happy with it
If I need to go back to OSI then copy the muls from the client\mulsbak directory back into the client directory and the F:\UOData directory