deadlock with vacuum full on 7.4.5

I have a table that is usually really small (currently 316 rows) but
goes through spasams of updates in a small time window.  Therefore I
have a vacuum full run every hour on this table.

Last night one of these vacuum fulls deadlocked with a query on this
table.  Both were stuck doing nothing until I did a kill -INT on the
backends doing the vacuum.

So my questions:
1) What can I do to avoid this?
2) What do I do next time this happens to get more debugging info out of
the situation?

My postgres version:

PostgreSQL 7.4.5 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.2
20030222 (Red Hat Linux 3.2.2-5)