vsftpd and mysql (pam problem?)

[Luca Ferrari]

Hi all,
I've followed line by line the instruction to configure vsftpd for using 
accounts coming up from a mysql database here:
http://www.howtoforge.com/vsftpd_mysql_debian_etch_p2

but when I try to log-in the server I always get an invalid password error. 
I've tried to check the mysql logs to see what query is executed, but they 
don't report anything (while there are queries executed via the mysql 
console), thus maybe it is something wrong with the configuration that does 
not query the mysql database.
Is there any way to see what pam is doing in order to try to understand the 
problem?

Any idea?

Thanks,
Luca