DST failing on 8.1.3

I'm running a production database on Linux (select version() =
"PostgreSQL 8.1.3 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 4.0.3")
I read that all 8.1.* versions are DST-compliant, and sure enough, my
development server, which runs 8.1.0, switched fine, as did my 8.2.3
database at home.
The production database was upgraded a while ago to 8.1.3 from 7.*. I'm
ready to upgrade to 8.2.3 to get the the benefit of all the development
since then, but before doing that I'd like to find out what's the
problem with the DST not taking.

The timezone is 'EST5EDT', and

SELECT CASE WHEN
timestamptz '20070401 0100'
+ interval '1 hour'
>= '20070401 0300'
THEN 'Wrong' ELSE 'Right' END;

returns 'Wrong'.

Are there perhaps timezone definition files that may not have been added
when upgrading from 7.*?

Thanks
Jaime

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