I don't have reforged myself so can't test anything, when you say you can't open it anymore I assume you mean in the world editor.
Do you get an error message when it fails to load, and if so, what is the message?
If you can't figure out the cause, the easiest way is to delete/replace files in your map one by one until the map can be opened again.
Note that some files are required by the world editor, so instead of deleting them you should replace them with with a placeholder file, you can create a new map in the world editor and use its files for this.
I'd start with deleting the object data files (war3map.w3a/w3h/w3b/w3d/w3t/w3u/w3q) and any imported files.
If that doesn't work replace the trigger files (war3map.wtg and war3map.wct).
After that try replacing the others (war3map.doo, war3mapUnits.doo, war3map.w3r, war3map.w3s, war3map.w3c).
By now I think your map should be openable again, so let me know which file was the culprit and I'll see if I can find the exact cause.