error Backing up DB

I am getting the following error when using pg_dump (v 7.0 on linux)

getTables(): relation 'client': cannot find function with oid 1654 for
trigger RI_ConstraintTrigger_7406341

And when I try and look at the functions using

/df

I get the following error -

ERROR:  Function 'oid8types(oidvector)' does not exist
        Unable to identify a function that satisfies the given argument
types
        You may need to add explicit typecasts

Is this familiar to anyone else???

Thanks

Graham