Implicit transaction not rolling back after error

I'm having difficulty locating the source of a problem our webapp has
been running into. Multiple Google searches have failed me, so I'm
hoping someone here can help troubleshoot.

When some clients (psql, the webapp) connect to our production
database, they become stuck in an aborted transaction after any failed
statement. For example:

    $ psql --version
    psql (PostgreSQL) 9.0.5
    $ psql test
    psql (9.0.5)
    SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256)
    Type "help" for help.

    test=> SELECT foo;
    ERROR:  column "foo" does not exist
    LINE 1: SELECT foo;
                   ^
    test=> SELECT VERSION();
    ERROR:  current transaction is aborted, commands ignored until end
of transaction block

Of course, there is no explicit transaction around the first
statement, but no commands can be issued until after a ROLLBACK.

Stangely, I don't encounter this issue if I connect directly from my
development machine.

    $ psql --version
    psql (PostgreSQL) 9.2.1
    $ psql --host $HOST test
    psql (9.2.1, server 9.0.5)
    WARNING: psql version 9.2, server version 9.0.
             Some psql features might not work.
    SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256)
    Type "help" for help.

    test=> SELECT foo;
    ERROR:  column "foo" does not exist
    LINE 1: SELECT foo;
                   ^
    test=> SELECT VERSION();
                                                       version
    -------------------------------------------------------------------------------------------------------------
     PostgreSQL 9.0.5 on x86_64-pc-linux-gnu, compiled by GCC
gcc-4.4.real (Ubuntu 4.4.3-4ubuntu5) 4.4.3, 64-bit
    (1 row)

I also don't encounter the issue if I connect to the running 9.2
daemon on my development machine either.

Our production webapp also suffers from this problem (which is how we
noticed it in the first place). It connects to the PostgreSQL daemon
through a Ruby library (pg) which wraps libpq5. I assumed the only
commonality between psql and our application was libpq5, so upgraded
it to a later version (9.2.2) with no luck.

Does anyone know what this might be? Is it a bug? A feature? A
configuration issue? I'm kind of at a loss at this point.

Thanks in advance for your help.

--
Stephen Touset
Senior Software Engineer
stephen.touset@onelogin.com