To learn to work with BDC (anod other MOSS stuff) you really have to first know to configure diagnostic logging; without this you are left with very little information to figure out what’s wrong.
Goto ‘Central Administration’ -> ‘Operations’ -> ‘Diagnostic Logging’ -> ‘Event Throttling’ and turn on the objects that you want to monitor. In this case, you may want to turn on ‘Business Data’, select ‘None’ and ‘Verbose’. You can also customize your log path so that it is not as long as the default value.
Then open the log file from “C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\LOGS”