Postgres problem on LedgerSMB (Ubuntu 10.10)

[Nigel Titley <..hidden..>]

Since a recent routine upgrade of postgresql a couple of days ago
LedgerSMB has stopped working. I get the following (or similar) error on
any operation that tries to write to the database

DBD::Pg::db do failed: ERROR: could not load library
"/usr/lib/postgresql/8.4/lib/plpgsql.so": /usr/lib/postgresql/8.4/lib/plpgsql.so: undefined symbol: do_convert_tuple at LedgerSMB/Form.pm line 1700.
Error!

UPDATE "parts" SET "onhand" = '9' WHERE id = 12465
ERROR: could not load library
"/usr/lib/postgresql/8.4/lib/plpgsql.so": /usr/lib/postgresql/8.4/lib/plpgsql.so: undefined symbol: do_convert_tuple

LedgerSMB has been working perfectly up to now. I believe the problem to
be somewhere in the postgresql server package and I have seen one recent
report of a similar problem in a different package to LedgerSMB but with
no resolution. I've done the obvious things like running ldconfig and
checking that the file exists and looks reasonably sane.

Is anyone else seeing this and is there a fix?

Thanks

Nigel