Thanks for the notice about the typo. That's fixed now.
Okay, so I've done some more testing this morning. I followed the instructions to generate the new_mame.xml, which worked. I then used that to generate the romlist in AM and got the same result.
I then generated a new xml from within mame which it exported to the UI folder. I then used that to generate the romlist in AM and got the same result once again.
I then chose to generate a new mame.txt from within mame and exported it to the UI folder. In this case I moved the mame.txt file to AM's romlist folder and loaded AM. It displayed the full range of 35k+ games, but when I clicked on them, they don't load, or respond at all.
I'm really confused and frustrated with this as I can't see where the error could be.