Hi there,
It seems yellowsn0w won't start as a daemon sometimes.
if you check your process list with "ps -e" command you can't see this daemon in running state. so if you start yellowsn0w by command(in mobile terminal) you can fix this issue. anyways this is beta released so just wait and see.

my baseband is:02.28.00 so this is not baseband version issue.

upgrading yellowsn0w to 0.9.4 sucessfully resolved this problem.
my network carrier detected, dial in calls work but dial out failed.