So they seem to have fixed it by changing the PHP version... I still don't get why it was working one second and then down the next though. Here's the message they've sent me:
I was able to resolve the issue on your site by adjusting it to run under PHP5.4. It looks like the issue was due to the php version, indication from the segmentation fault which is by definition an unhandled error most likely related to PHP and the set environment on the account.
I'm not sure what version of PHP they changed from but have asked them.
