When accessing wiki pages that include math formulas, a request is sent for each formula to a wikimedia mathoid-server, of which there are several made available as a public service. When the server is pummeled by too many requests/sec, it rejects additional requests. That is why sometimes you'll see the red error messages in place of formulas one day, yet find everything works great the next.
Please let me know if you still encounter the red messages.
If they do continue, would be great if someone is willing to set up a server on the cloud as a mathoid-server of our own. (On ubuntu, where the wiki is hosted, it was not completely trivial, so I aborted my effort.) Just let me know.
Thanks!