Negative caching of access denied errors

Negative caching of permission denied errors seems to be really really
persistent, despite reloads, depite restarting squid, despite rebooting the
machine (not because of this problem).

When I have netscape set to use Squid I get broken images on a particular page
I'm fond of, but when I set it to not use Squid the images work fine. If I
check the image I see it's a permission denied error from squid and reloading,
shift-reloading, just makes it flash with the same error without even
contacting the server.

How do I convince squid to flush these cached errors?

Here's the error:

> ERROR
>
> The requested URL could not be retrieved
>
>
>
> While trying to retrieve the URL: http://flotsam.slashdot.org:81/title.gif
>
> The following error was encountered:
>
> Access Denied.
>
> Access control configuration prevents your request from being allowed
> at this time. Please contact your service provider if you feel this is
> incorrect.
>
>
>
> Generated Fri, 21 May 1999 16:13:33 GMT by localhost (Squid/2.1.PATCH2)
Received on Fri May 21 1999 - 10:44:02 MDT