Most likely. Works perfectly here, and I'm not sure what you did. What's set as "configuration path" in the Arcade Setup dialog? Does it match QMC2's configuration path?
The actual file that it's trying to load is logged to the "console". You should see an obvious difference when launched through QMC2 or directly when your setup is wrong (for whatever reason). An empty list most likely means that it simply can't find the machine list cache file (or its filtered pendant).
I also can't reproduce your reported issue.
So... From left to Right : My folder config for QMC2-MAME, the one for QMC2-Arcade, my Category list, my category list in the file chooser for QMC2 Arcade.
The last list contains a "?" entry, the catver file i use have no reference to a "?" category, your category.ini file has one when used (well to be exact QMC2 auto classify any driver that has no category in it, but my catver has everything categorized), hence i deducted that it might be taken from it, or something like that.
I think i had it wrong, and you might have to remove "?" when there is no uncategorized driver, but it's a very low priority thing. You can remove my bug report.
Don't be mistaken for the other issue, even though you can't see it on these screenshots, i have some category selected, and there is a not empty list when i launch QMC2-Arcade directly.
Only problem is when i launch it from QMC2-Mame.
Auto-play works fine here, also tested successfully on Windows, so I have no idea what could be causing this for you. Are you using the official VC++ builds (*)? And which theme are you using?
(*) Note that MinGW builds will not support QML video at all, unless you build/deploy qt-mobility for it. Trying to start QMC2 Arcade with "-video on" in this case would already fail loading the required QML imports, though.
I use the officials VC++ builds, yeah. Videos works fine, but i have to click on the play icon.