RT: Transaction not committed

Hi All,
My 3.6 install of RT Stopped working a few days ago. I can no longer
create tickets via email.
To my knowledge nothing was changed with the RT install. However the
mysql database was upgraded from 4.1.14 to 4.1.21. The database appears
to work fine for everything else though.

In the message log i have the following error :
RT: Transaction not committed. Usually indicates a software fault.Data
loss may have occurred (/opt/rt3/lib/RT/Interface/Web/Handler.pm:194)

In the maillog i have the following errors :
sendmail[14991]: k78BA9fp014990: to="|/etc/smrsh/rt-mailgate --queue ‘IT
Support’ --action correspond --debug --url http://rt.cel/",
ctladdr=rt@cel (8/0), delay=00:00:01, xdelay=00:00:01, mailer=prog,
pri=31300, dsn=4.0.0, stat=Deferred: prog mailer (/usr/sbin/smrsh)
exited with EX_TEMPFAIL

Want i want to know is how do i go about debugging RT to find out what
might be causing these errors. I have set $Develmode to 1 in
RT_SiteConfig but this does not produce any additional logging info.
This one is really baking my noodle ;-).
Thanks in advance for any help comments.
Regards,

Ian Clancy
IT Co-ordinator
Connaught Electronics Ltd.
Dunmore Rd,
Tuam,
Co. Galway,
Ireland.

P : ++353 93 23151
F : ++353 93 23110
E : mailto:clancyian@cel.ie
W : http://www.cel-europe.com