I don't know if this will help much, but I was having similar problems while running Debian (Woody) linux. It seems that initially, everything was fine, then the next day it didn't work. I no longer remeber exactly what happened, but I do remember (this is the part where I try to be helpfull) that installing SWAT was very helpfull for browsing the SAMBA configurations. SWAT is an HTML interface for SAMBA. It sort of gives it a GUI frontend that I, as a beginner found very helpful for troubleshooting.
It was very easy to use and setup, so don't be shy.