Give me some suggestion

Hello,
I 'm a new postgresql user and now I have some problem about it.
I'm not sure this problem is a bug of postgresql or not.
My problem is I have to read a text file ,processing and keep it into
database.
Each text file is about 50,000 records, the process can be insert,update
and delete.
I had random check and found that in the process of updating some can not
be updating.
It's happen with some text file ,but some are not.
I really don't know what is the cause of problem but it's not about
bussiness logic because
sometimes it's updating correctly.
I had investigate the log file of my program but there is nothing (I
wrote the log file to show if
it had an Exception or SQLException,so i'm quite sure that my sql
statement is correct.)

I used postgresql 7.4.6 , Platform is SUN Solaris9 , my program is java
web-application (on tomcat4.1).

Thanks,
Manee