This has been an issue with DDAY for quite awhile. When it reaches maximum load time (which can happen on some over-loaded servers) the plugin crashes with a FATAL ERROR crash. This prohibits the rest of WordPress from loading. The the user it appears the site is dead or been hacked etc.
I prefer this plugin over all others and would rather use it but I just cannot take a chance on the blog being down again because DDAY won't load. I think I mentioned this once before. When I saw the version had changed I tried it again. Same issue is still there.
DDAY needs a method for a graceful exit. Perhaps a trigger for an error message that loads in the widget window that says something like, "Ooops! Plugin unable to load calendar data. Try again later."