As a result of a configuration change introduced during last night's maintenance window, the proxies are erroneously reporting that some people are over the per-user Internet quota. The problem is specific to the staff and student wireless networks; it does not affect computers connected to wired network sockets. People on these networks may erroneously receive an ERR_IDBLOCK error. (Note that an ERR_IDBLOCK error message received on a public lab computer is not related to this problem, and is almost certainly correct).
The problem is directly related to the load on the proxy servers, and started being triggered about mid-morning. Since then we've been trying various workarounds to better handle the load. Unfortunately none have been successful.
At about 14:45, we partially reverted last night's configuration change. We are continuing to monitor the situation.