Disabling Automatic Redial

I have 2 comps on a LAN, both of which connect to ISP via the client.
Everything works well. On both comps, the Internet Options/Connections are
set to "Never dial a connection"

The problem is that when we are intentionally off line, occasionally
something is causing an (automatic?) redial. I have no idea which machine
is doing this, or how to find out (in a reasonable amount of time). It is
causing a real problem with our
fax setup, however.

Is there some way to prevent this auto redial, or at least find out what is
causing it?

Both comps are WinXP, SP2, IE6 and OE6 - pretty standard otherwise, although
both have
acquired a number of special apps over their lifetime (2 - 3 years).

Appreciate any suggestions.

Dave