23.5.2009 I got first sound out of Mp3 player that was controlled by arduino. I used VMUSIC2 module, which can play mp3 files from USB memory stick.
I needed to update the firmware in order to make it working with all available commands (for example volume control).
VMUSIC2 module is not very well documentes so big thanks goes to Arduino forum for good hints (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1187669098) and http://www.instructables.com/id/Getting-started-with-VMUSIC2
After updating the firmware, the VMUSIC2 started behaving like the manual described.
After reading the manual more carefully, I noticed that the MPEG3 chip was actually a product of VLSI solutions - A Finnish company located about 300 meters from my working place at the same campus.
Well now I certainly know where I will call if I am having problems with VMUSIC2 mp3 decoding :-)
See also following links for useful information: http://byungjun.pe.kr/xe/?document_srl=20431 and Vmusic-tips-and trics
Eventually, I did not use VMUSIC2 because all USB sticks I found were too big to fit properly to the robot chassis I was building. Instead I used MP3 Trigger with microSD card.