unable to add or delete from table

I'm using a postgresql database as the back end for opennms. Everything
was running fine until I had to do some tuning a few weeks ago
(basically deleting old nodes, unmanaging interfaces, etc.) I did all of
this via the web ui that comes with opennms. However, I discovered a
couple of days ago that I am no longer able to add or delete nodes. It
appears that the node table is locked and nothing I have tried has
allowed me to modify this table. I have been able to work with the other
tables in the database just not the node table.

I am certainly not a sql expert but everything I have tried to date has
failed.

The command that I am running to delete a node from the command line is
as follows:

delete from node where nodeid=19;

This command just hangs at the command line and a ctrl-c jumps me out of
it. All that appears to be logged is a "query cancelled by user".

I have tried reindexing the table, running a vacuum on the table and the
database, all to no avail. I am able to run similar commands on other
tables to delete unwanted rows.

Any ideas on what I am missing here?

Thanks,

Craig Russell