The pilots made no mention of an explosion - at least
not that's been published. The pilot just said "technical
difficulties". Also since almost the entire complement
were Moslems it becomes less likely that it was Islamic
terrorism (although there are factions that despise
"ordinary" non-rad Moslems).
The plane was reported to have had "instrument
problems" the day before which were theoretically
repaired in Bali. You've gotta wonder though, maybe
the problem wasn't with the instruments ... but
instead the instruments were accurately reporting
some evolving mechanical issue.
In any case, it crashed not THAT far offshore and they
ought to be able to recover the recorders pretty quick.
The newest ones monitor a huge number of parameters.
As I remember, the original 737 model had a bizzare
software problem that - under a very narrow combination
of events - would throw the engines into reverse thrust.
At least one, maybe two, crashed (also in that part of
the world) before anybody figured it out. While Boeing
never admitted it, this was likely some software test
code that was never removed before production.
A modern airliner is more complex than a spacecraft
and that means not every combination of factors can
be tested for. I guess we can always fall back to a
Sopwith Camel ... although I'd trust a DC-3 even more,
simple and tough as nails. I've seen jet conversions
of those (gotta be split and stretched about 6 feet for
balance) ... STILL loads of DC-3's in service.