Player :
Softsqueeze 3.4 (now 3.5)
Audio buffer size = 384000

Slimserver audio config :
Encoding using lame
Lame quality level : 2
BITRATE LIMITING : 64kbps

Comments :
My work internet connection is very bad so I increase Softsqueeze audio buffer size to prevent silence during playback.
When player try to buffer short song (<50 seconds), buffering stops when all song is buffered and player don't start playing because buffer is not full.
I think it's a slimserver problem : slimserver must buffer next song after current one is finished then player will be able to fill its buffer and playing buffered short song.