The solution will work for majority of cases. However, various versions of InfoSelect are using different document delimiter texts. AllMyNotes is configured to use "=-=" delimiter string. While older versions of InfoSelect use "--", to correct it use steps below:
1. Exit from AllMyNotes
2. Locate AllMyNotes.ini file, open it with Notepad
3. Find "ImportingDocBreakMarkerStr==-=" text line. And change it to whatever you want for example, to have delimiter char "--" (as it was before) would be enough to change this line to "ImportingDocBreakMarkerStr=--"
4. Save changes.
5. Launch AllMyNotes, do import from .txt file.
P.S. The solution above will work also for many other applications that can export data to .txt file, you just need to configure AllMyNotes Organizer to use correct delimiter string using steps above. Enjoy!

P.P.S. This article refers to version 2.40 build 428, if you are using older version you are welcome to download it by this link