Sorry for the recent downtime. Still much to do but we have the site updated, secure and back online. Expect more changes.
For anyone coming after me who has this problem, you need to download the latest .ahk file for MAME that's in the downloads section and put it in HyperSpin\Modules\MAME. I've solved this issue for now by rolling back a few versions - using MAME0210 with 215 roms, and it seems to be fine so far. You can download no-nag versions (removes warnings and machine info on game startup) from the downloads section.
I updated my MAME roms to 215 from 0170 recently, since there are 1/2 more games I'm interested in available now and due to increases in accuracy etc. Just thought it was a good idea, but... The latest AHK/module file from the downloads section (labelled for 212) seems to not work with 215, but it worked with 0170. What do I do? Is there a AHK file that works with MAME0215 that I'm missing, or do I need to wait. If so, how long? (I'm getting the .ahk error that means the .ahk file is out of date. I had this problem with 0170 and sorted it with the 212 .ahk file.)