MO3's inside a RAR, mass-tagged on artist field from the library view, then removed the artist field (note that Overridden wasn't ticked when reopening Track Info!), pressed apply and XMPlay crashed.
Ah, I think I see what the problem might be! There was a little bug in the mass-tagging. Here's an update to try...
www.un4seen.com/stuff/xmplay.exeRegarding the unticked "Override" thing when there are overridden tags, the thinking behind that was that you would have to tick it to override the overridden tags

... But it'll now be ticked if all the selected tracks have overridden tags (it'll be left unticked if any don't).
when I use the Find track(s) dialog, type (for example) "kätilöt" and press enter, it changes to "kätilöt". After closing, the playlist shows the ä and ö properly.
Oops, that should be sorted in the update above.
On an unrelated subject, when I did the 'Add directory' on M:\Music, it loads some dead entries (H:\Blahblah\File.ext) for an unknown reason. 'Ignore playlists & shortcuts' is enabled.
Does that happen if you remove all plugins, notably Winamp plugins? It could be one of them accepting the file extension.
Just had a look at the playlist in a text editor. It has replaced a song name with a string of garbage ~692884 characters long. Will upload a playlist very soon. And possibly the file in question too.
xmplay_jace_WTF.rar uploaded. I don't think you'll have trouble finding the line in question. 
Yep, that'd explain it

It'd result in the UTF-8 detection failing, due to non-UTF8 sequences in the garbage. I'm not sure how the garbage got there though - does it appear in the playlist right from the first time you save it?
The file in question seems to be "M:\Music\Web Downloads\herkk%e4%e4.ogg". Does the garbage still appear if you remove that file from the directory, before adding the directory to the playlist?
No, I want them in alphabetically order.
Oh, in that case you shouldn't have a problem. It's the non-sorting option that's been removed

You can sort the results by title or filename by clicking on the column headers.
Is that with XMPlay on top?
Yes, it is.
Ok, I think that's always happened. I'm not sure if there's anything that can be done about it.
With a fresh config, it is "loop detected" by default. Thinking about it, I did have a default path setting with mod and loop options, so this may have overriden the setting.
That'd explain it. The auto-loop setting is now part of the MOD saved settings, but in settings saved previously, it'll be 0 ("never"). I guess that's not really very nice, and the auto-loop setting probably doesn't really need to be saved anyway, so I've removed it from the saved settings in the updated EXE above.
Uploaded as nevi popup.rar 
Ah yes, I see now. Those are saved settings from a previous version, before the "Effect has a tail" option was added. With that option added, the current Winamp DSP config no longer matches the saved config, and so it gets reloaded. The saved settings will need to be updated. I've added an "Update" option (via a right-click menu) in the updated EXE above, to make that pretty simple - "Load" the setting and then "Update" it

Unfortunately, I think you'll probably need a more powerful CPU to smoothly run the vis in fullscreen. As a last resort, you could try lowering your monitor resolution.
Could XMPlay do the resolution switching?
I've not tried that yet, but the option may well appear in a future update.