That is what happened to Mars Climate Observer
1999 was not a good year to be a Mars probe.
http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1998-073A
Burning up may also explain why Beagle 2 has yet to be found on the
surface.
I recall that Beagle 2 did not get the money and support its creator
said it needed to be completely successful? Would throwing more
money at Beagle 2 have made a difference? Is he still working on a
Beagle 3 and would it be any better than MSL at finding Mars life?