I may be the Cox/MojoHost client Brad referred to above (or I may be one of many). I had numerous calls in with Tier2 tech support at Cox on Thursday as this was going on, and relayed stuff back and forth between the Cox tech and a Mojo tech on ICQ. What it comes down to is...
Brad's exactly right. This is a Cox issue, whether they choose to admit it or not. I'm back to hammering Cox (that sounds really bad) on this issue today. I don't really care if I personally have the problem, I can always drop the MTU setting on my router. But if CUSTOMERS can't reach my server, that's where I draw the line and I'm not backing down on this.
Kudos to MojoHost and their exemplary tech support staff. We'll see if Cox can clear this up, because it's getting very old very fast.
(P.S. Here's a good line to use when something like this happens (multiple people report outage). When the first-line tech support person says "it could be your wireless router," respond with "are you suggesting all the other people who are having the exact same problem are parked outside my house, leeching my wireless? Because I'm looking out the window and I don't see anyone." You'll get something along the lines of "ummm, errr."
Matt @ MojoHost said it best... "Minimum wage, minimum work.")