PL/SQL bug?

Oracle7: 7.0.12.1.0
PL/SQL: 2.0.14.0.1
HP 9000/897
HP-UX 9.0

It seems that if I try to access two tables in different schemas via PL/SQL, it doesn't work. (One update / one select - I haven't tried other permutations). Has anyone else come across this feature and is there a workaround / patch for it? Yes, I _do_ have access to the tables; I can update quite happily from forms or SQL*plus; it's just the PL/SQL procedure which doesn't work....

-- 
                               John Peach
                           Chevron (UK) Ltd.
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