One place to check might be the Samba log files:
cd /var/log/samba/ , then li (See what log files are available)
then "su" from a terminal then,
tail -f /var/log/samba/????? will keep a running log (constantly updating) of whatever log you want to sniff at
You can see all of the log file using an editor (in su mode)
Hope this gvies you a starting point!