I recently opened a MindManager file and got this XML Processing error:
Followed by this error, even though the file was in the folder, and then the file not opening.
After some web searching, found this is a known error with MindManager Files and the recommended fix was to send the file to MindManager Support for them to remove the offending character. I didn't have time for that so tried fixing myself and it worked.
NOTE: Everything that follows worked for the error I encountered, there may be other errors of this type it doesn't help. Be sure to try this on a copy of your file as it may wreck it!
Copy the file and change the file extension from Filename Copy.mmap to Filename Copy.zip
XML Notepad Editor failed with a similar error to MindManager, confirming the issue, but gave more information to confirm the cryptic MindManager error dialog.
It showed the offending item was in Line 3, Position 196896, thus the MindManager (3:196896) reference.
To get there open the XML with a text editor that allows you to Search a line for a specific character location like Notepad++ Search > Go to… (Offset) seen below. (Unfortunately, the default windows Notepad only has Go To line number, not location)
In my case the PlainText field had some odd characters. I replaced these with 'REPLACE TEXT' and saved the changes to update Document.xml.
Renamed from Filename Copy.zip back to Filename Copy.mmap the file opened OK with a topic showing REPLACE TEXT.
In my case I had drag and dropped a website URL into the map to make this topic. Seems something in the web page description upset processing of the xml by any reader. Worked for me, hope it helps others!