I've pasteurized a few batches of cider over the last year, as well as some sodas and tepache. I have had 2, maybe 3 bottles explode. One was when I heated the bottles up to temp in the water...I do NOT think that's a good idea. Another, I know was overcarbed. I have been starting at room temperature and using a pressure canner body for the water heating with a false bottom that came with it, so the bottles don't directly touch the bottom. I heat the water to temperature, remove from the heat, place the bottles in and use the cover, not pressure locked, but just to cover loosely in case a bottle blows.
I'm betting yours was overcarbed. A week, depending on your yeast and amount of fermentable sugar, could be way too long. My soda and tepache carb in less than two days. I don't always pasteurize my ciders if my SG goes from around 1.05 down to 1.005. If my FG is more than 1.010, I'm going to pasteurize.
So, here's my question for you: did you have a tester bottle of any kind? You need to monitor the progress of the carbonation and err on the side of safety. Some use a plastic soda bottle. I just use one or two of my batch bottles. I'm thinking that you probably should have pastuerized your batch after 3 or 4 days.
Anyway, it's ALWAYS a good idea to have a lid partially covering the pot...it will at least partially contain glass and mess. It does happen, though. Here's my journal entry from my most recent bomb on July 11th:
http://mmmbrews.wordpress.com/2014/07/11/day-128-gushers-and-bottle-bomb/