I spent some time troubleshooting problem with streaming music server that I have. The music server contains many MP3 files. Some of the MP3 files were created long time ago with Real Jukebox Plus (do not laugh - it was before WinAmp). On playlists I have, sometimes SL Client would play the music, sometimes it would not! I had no problems with the music server if other music player clients were used, such as the WinAmp player. After much troubleshooting, I discovered the SL Client Music player does not like the MP3 data created with Real Jukebox Plus! I submit the problem to LL, but I don't know if they do anything.
I post this for information if other people have streaming music problems. I guess I must re-rip my music CDs with WinAmp.