Backups with pg_dumpall do not restore all data

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POSTGRESQL BUG REPORT TEMPLATE
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Your name : Mike Martin
Your email address : mike(at)bristolreccc(dot)co(dot)uk

System Configuration
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Architecture (example: Intel Pentium) : AMD duron

Operating System (example: Linux 2.4.18) : Linux 2.6.3

PostgreSQL version (example: PostgreSQL-7.4.2): PostgreSQL-7.4.2

Compiler used (example: gcc 2.95.2) : n/a

Please enter a FULL description of your problem:
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There appears to be a problem with pg_dumpall.
I maintaain a DB of around 6-7 tables, being a finance and contacts
system.
If I use pg_dumpall, two of the tables are restored without any data.
These are linked together.

Even more curious the data is dumped into the dump file.

If I use pg_dump there is no problem.