Every time I try to open an existing map in the editor, the program begins to show the error "Attempted to read or write protected memory" over and over and either crashes or needs to be shut down manually. This ONLY happens if I open a level that has had an AI grid generated.
There is a workaround: When the AI grid is generated, it creates the 'aigrid.data' file in the "\mods\[mod name]\AI" folder. This file needs to moved to the "\mods\[mod name]\Level\[level name]\AI" folder. (You may need to create this folder first)
Once you take this step, it seems to fix the crashing issue for that level - other levels need to have the same file moved into their AI folder in order to open properly. However, updating the AI grid for any level will update the file into the wrong location - it has to be moved manually into the proper level each time to update the grid properly.
I know this bug (or at least a very similar one) has already been reported, but I haven't seen anyone from Larian acknowledge they know about it. Searching on the forums for the bug seems to only bring up unrelated posts.