Forum OpenACS Q&A: Strange errors with sec_read_security_info

I've all of a sudden started getting the following errors, about
once every half an hour:

[05/Mar/2001:13:38:21]
    Error: Ns_PgExec: result status: 7 message: ERROR:  Cannot
insert a duplicate key into unique index
sec_browser_properties_pkey

[05/Mar/2001:13:38:21]
    Error: dbinit: error(10.11.12.2:5432:celebrityblvd,ERROR:
Cannot insert a duplicate key into unique index
sec_browser_properties_pkey
    ): 'select sec_rotate_last_visit(24003, 983828301)'

[05/Mar/2001:13:38:21]
    Error: Filter sec_read_security_info returned error #1:
Database operation "1row" failed (exception NSDB, "Query was
not a statement returning rows.")

[05/Mar/2001:13:38:21]
    Error: tclop: invalid return code from filter proc 'Critical filter
sec_read_security_info failed.': must be filter_ok, filter_return, or
filter_break

These four error messages always occur in succession,
obviously with different values sent to sec_rotate_last_visit every
time.  Does anyone have an idea why these are occurring?
These errors just started a few days ago, and everything was
working fine before.

Here's my setup:  I have two aolservers running, using the same
database, with AOLserver 3.1 (i think), postgres 7.0.3, and redhat
7.0.

Thanks in advance for any help you can provide!