Undoubtedly you've already gotten your answer, but my best guess is that an animal dug her up recently releasing this smell.
As the weather cools, many folks will open their windows, whereas before they may be using hvac/air conditioning to cool their home.. Also JM may have used lime, bleach, etc. to delay the decomposition process. Serial killer Israel Keyes, used drano to expedite the decomp process of his victims. The abandoned house where IK left the Curriers(VT) was later demolished. The demolition crew smelled the odor and chalked it up to a dead animal and hauled them to a landfill with the construction materials..
Serial killer Anthony Sowell; the Cleveland strangler, kept his decomposing victims in his house. He lived next door to a sausage factory. They were fined numerous times due to the foul odor.. You can't make this stuff up...
http://en.wikipedia.org/wiki/Anthony_Sowell
Anthony Edward Sowell (born August 19, 1959) is an American serial killer, identified in press ... I thought I was going to die. ... Sowell worked in a factory until 2007 when he began collecting unemployment benefits. ... she moved out that the smell was from Ray's Sausage Shop, located next door to the Sowell residence.
http://murderpedia.org/male.K/k/keyes-israel.htm
Keyes reportedly broke into the Curriers' home on the night of June 8th and tied them up before driving to an abandoned farmhouse, where he shot Bill Currier ...