We're going to be taking the proxy server (cache1) down for urgent maintenance this afternoon. The idea is to move its hard disks to a new machine in order to try and resolve the instability of late.
This change should be transparent to all users. We've already changed the proxy.pac file and wwwproxy alias to point to the backup proxy server (cache2). Those users who've had their browser window open since yesterday might need to close it in order to pick up the change -- everyone else should already be using the right server.