long idle connections causing problems?

Just in the past month or so (no code changes, server changes that I
know of, etc, for the last six months), I've started getting errors like:

org.postgresql.util.PSQLException: Unknown Response Type 8
at org.postgresql.core.QueryExecutor.executeV3(QueryExecutor.java:192)
at org.postgresql.core.QueryExecutor.execute(QueryExecutor.java:100)
at org.postgresql.core.QueryExecutor.execute(QueryExecutor.java:43)
at org.postgresql.jdbc1.AbstractJdbc1Statement.execute(AbstractJdbc1Statement.java:517)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:50)
at org.postgresql.jdbc1.AbstractJdbc1Statement.executeQuery(AbstractJdbc1Statement.java:233)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:205)

The particular response type will change each page load.

Doing a process query will show a number of long-running idle postgres
processes for that particular website. Other site pools don't seem
affected, but this one is heavier load than the others (still only ten
thousand hits a day or so). If I kill all the idle processes for the
site, one of them will still remain:

24619 ? S 14:21 postgres: xxxxxxx xxxxxxx 127.0.0.1 idle

Which I then have to kill -9... which then requires a restart of tomcat
to hook back up.

possibly relevant version numbers?

psql (PostgreSQL) 7.4.7
Apache Tomcat/4.1.31
Apache/2.0.51
Fedora Core 2, kernel 2.6.9

Any thoughts on what configuration I should be looking at, or if
there's something I just dearly need to upgrade, ...?

Thank you for your time. :)

-kaolin fire
-http://erif.org/code/detritus/