I am unable to import 2 mp3 files from a list of 10 - the other 8 no problems.

This is the error message I get:

Cannot import C:\Users.mp3 file attachment - Out Of Memory! File Size - 12156928.

Please note that all file attachments from currently edited document must be loaded in to the RAM. This message means that your system is unable to allocate free RAM for loading file attachments. Actually this is quite rare case, for example, AllMyNotes is able to handle shortage of subsequent big memory chunks if system is able to provide smaller chunks instead. Try to increase size of virtual memory, it may help.

Also, as an alternative solution, I'd recommend to use hyperlinks to local files instead of attaching big files to AllMyNotes.