Well, I have an m3u playlist I created in XBMC saved in my xbox, playing songs off a share. It plays just fine. Here it is:
#EXTM3U
#EXTINF:0,AC/DC - Highway to Hell
smb://192.168.0.2/Music/ACDC/Highway To Hell/01 - Highway To Hell.mp3
#EXTINF:0,Cake - Satan Is My Motor
smb://192.168.0.2/Music/Cake/Prolonging the Magic/Cake - Satan Is My Motor.mp3
#EXTINF:0,Tenacious D - Explosivo
smb://192.168.0.2/Music/Tenacious D/Tenacious D/Tenacious D - Explosivo.mp3
#EXTINF:0,George Harrison - Between the Devil and the Deep Blue Sea
smb://192.168.0.2/Music/George Harrison/Brainwashed/Harrison, George - Between the Devil and the Deep Blue Sea.mp3
Here's an excerpt from the playlist that does NOT work, except for the first track, where I changed "D:/My Music/" to "smb://192.168.0.2/Music" manually. This playlist is also saved on my Xbox:
#EXTM3U
#EXTINF:165,Nat King Cole - Quizas, Quizas, Quizas
smb://192.168.0.2/Music/Nat King Cole/nat king cole - Quizas Quizas Quizas.mp3
#EXTINF:138,Dean Martin - Cha Cha Cha d'Amour
D:/My Music/Various Artists/Ultra-Lounge, Vol. 09 - Cha-cha De Amor/Ultra-Lounge, Vol. 9 Cha-Cha De Amor - 12 - Dean Martin - Cha Cha Cha d'Amour.mp3/
#EXTINF:269,Wes Cunningham - So It Goes
D:/My Music/Wes Cunningham/12 Ways to Win People to Your Way of Thinking/Wes Cunningham - So It Goes.mp3
#EXTINF:187,Nouvelle Vague - Just Can't Get Enough
D:/My Music/Nouvelle Vague/Nouvelle Vague/02 - Just can't get enough.mp3
#EXTINF:204,Get Up Kids - Close to Me
D:/My Music/Get Up Kids/Eudora/The Get Up Kids - 04 - Close to Me.mp3/
#EXTINF:175,Five Iron Frenzy - Mama Mia
D:/My Music/Various Artists/Five Iron Frenzy - Mama Mia (ABBA cover).mp3
#EXTINF:149,Danko Jones - Fucked Up
D:/My Music/Various Artists/danko jones - fucked up.mp3/
I moved the above playlist to a location on my PC, and shanged the "Playlists" bookmark in XboxMediaCenter.xml to point to it. Same thing. First track plays, the rest don't.
Also, one of the first things I did was reverse the slashes in pathsubstitution. This way doesn't work:
<pathsubstitution>
<substitute>
<from>D:\My Music\</from>
<to>smb://192.168.0.2/Music/</to>
</substitute>
</pathsubstitution>
Nor does this way:
<pathsubstitution>
<substitute>
<from>D:/My Music/</from>
<to>smb://192.168.0.2/Music/</to>
</substitute>
</pathsubstitution>
Clearly, what I need pathsubstitution to do is find every instance of "D:/My Music/" (as you can see, from the second playlist above) and replace it with "smb://192.168.0.2/Music/" (as you can see, from the first playlist above). I assumed that the latter configuration of the AdvancedSettings statement was the one that made more logical sense, so I posted that - rather than the former, with the reversed slashes, which didn't work either, which I'd already tried before posting any messages anywhere.
Per jmarshallnz's note on my bug report, I have included a full debug log.
So... any other ideas, or is this an honest-to-goodness bug?