error viewing a Plone site while not logged in

I just got this error trying to view http://plonedev.uwosh.edu/grants in Safari (but not in Opera):

We're sorry, but there seems to be an error…

The error has been logged as entry number 1296577625.350.149377437986.

If you need to report this to the site administration, please include this entry number in your message.

The site looks fine if I look at it via the ZMI (and am authenticated via the Zope instead of via the Plone site's LDAP PAS).

When I looked at the site's error log, the error's traceback was:

Traceback (innermost last):
 Module ZPublisher.Publish, line 110, in publish
 Module ZPublisher.BaseRequest, line 583, in traverse
 Module Products.PluggableAuthService.PluggableAuthService, line 233, in validate
 Module Products.PluggableAuthService.PluggableAuthService, line 559, in _extractUserIds
 Module Products.PluggableAuthService.plugins.CookieAuthHelper, line 121, in extractCredentials
 Module base64, line 321, in decodestring
Error: Incorrect padding

The solution was to clear Safari's browser cookies for the "plonedev.uwosh.edu" domain.