I reproduced that error following your description (except using the files "RAM:Test" and "RAM:Test2" - lazy as i am ;-)
I did it twice:
1. Typing "ed RAM:Test", typing something, saving and closing MicroGoldED. But: I won't get my shell back - it is still blocked. So i had to open a new shell and type "ed RAM:Test2". Guess what happens? Right - the old file is opened (RAM:Test).
2. I used "RUN ed RAM:Test" etc. The starting shell in this case is of course usable after starting MicroGoldED, I can close the Editor after typing text in the first "RAM:Test" file and start it again in the same shell with "run ed RAM:Test2". And - yes - same error, it is opening the old file. When I close the editor again and then try to close the starting shell (which is still "usable", i have a prompt etc.) the shell WON'T CLOSE with a message saying "Process 4 is ending" ... for ever.
So, in both cases there seem to be problem with the detachment from the mother shell or general process handling of MicroGoldED - this is why i supposed it might be a part of that error. BTW: This is with OS4.1.