I don't know if it'll help, but here's an update with a little modification to try...
Bingo! That fixed it.

Btw., seems you forgot to increase the version number. The \stuff\xmplay.exe release from 2008-01-20 already was at v3.4.2.23.

[...] with the time display in frames mode, do you see it flicker to MOD mode (bpm/etc) while seeking in an MP3?
I didn't notice it until you asked, since it's quite hard to recognise unless you closely watch the timer. But yes, I can confirm that the flickering happened with the previous \stuff\xmplay.exe (2008-01-20) exactly as you described. It doesn't appear with the current version, and also I wasn't required to alter the ouput buffer.
Thanks, Ian. Very much appreciated.

spellchecking seems to be working fine here

Well, it doesn't for me. Maybe it's due to my browser (most current Opera, just updated today), or my AV application. Used to work previously, so I'll have to see...