[squid-users] Unknown error/warning in cache.log

Hello,

I found an error or warning in my cache.log:

"temporary disabling (Bad Gateway) digest from localhost"

Squid is configured to use an other (Anti-virus-)Proxy on localhost.

Where can I start searching for the reason of this log-entry?
What exactly does it mean?

Thanks a lot!

-- 
    <) .--.
    )#=+  '
   /## |     .+.                                   Greetings,
,,/###,|,,,,,,|,,,,                                Michael