Can't Create Tickets

Our RT3 system has been working fine for a couple of years now without
problems, suddenly last weekend the web interface slowed down
drastically. That cleared up over the weekend however and for some
reason (with no human interference), the ticket system has become unable
to receive emails sent to our support inbox

Linux 2.6.18-8.1.14.el5 #1 SMP Thu Sep 27 18:58:54
EDT 2007 i686 i686 i386 GNU/Linux

Perl 5.8.8, RT 3.6.3, !DBIx::!SearchBuilder 1.48, Apache 2.2.3, Mysql 14.12