MP just confirmed that mpex.co is under DDoS, but trading goes on normally whole day using proxies like:
mpex.5gbfree.com
mpex.host56.com
mpex.coinbr.com
If using pyMPEx , change the url in source code. As long as you verify the reply GPG signature (recent pyMPEx does), and make sure you got reply with different date/signature every time, you are 100% safe using proxies.
My suspicion is that MPEX is down so people don't pull money to cash out on the price hike.
mpex isn't down, just that url
try
http://mpex.coinbr.com or any of the other proxies