Mailscanner dies on some "corrupt" files

[Ramprasad]

This happens rarely but I dont know what is the real reason

I use Mailscanner + postfix + spamassassin. Everything seems to run
properly. Suddenly mailscanner would stop scanningany more mails from
hold queue and Mailscanner processes go defunct 
When I start Mailscanner again in debug mode I get

"Can't call method "DropFromBatch" on unblessed reference
at /usr/lib/MailScanner/MailScanner/Postfix.pm line 332.

I have to find which file it is looking at by puting debug statements in
Postfix.pm and find out which file it is and remove it from the hold
queue 

Thanks
Ram