'Tuple is too big' Error

Hi,

Using phorum (www.phorum.org) based on PHP, I am getting the following error
when trying to insert a message in the PosgreSQL 6.5.3 database:

ProcessQuery
ERROR:  Tuple is too big: size 12440
AbortCurrentTransaction

(obtained from the log). Can anybody tell me where to find proper
documentation to raise whatever parameter is necessary to avoid this
problem?

Thanks a lot,

Christian Pomar

Please, note that my reply mail has the #NOSPAM# token to avoid spam; just
remove it before sending email.

Thanks again