I have a farm in which, for the last two seasons (of a fort that so far has only existed three seasons), the dwarves have simply refused to harvest the fully-grown plants. Considering that it's autumn, I was rather displeased to notice that my dwarves were letting my plump helmets simply rot in the fields, and accordingly I investigated. I had a food stockpile with plenty of room, I had a barrel surplus, I had a farmer who also had plant gathering enabled, I had "All Dwarves Harvest" set, and the farm was completely accessible.
With a bit of playing around, I found that the "Harvest Plants" job WAS being generated and taken by the dwarves, and they would indeed go to the farm and stop over a plump helmet, but they would stop the instant they reached the plant and change their minds, choosing instead to go off and do something else instead. I naturally attributed this to dwarven laziness and tried again, and watched it happen again, and again, until finally I disabled every job on my farmer except Farming (Fields) and Plant Gathering, and watched him as he went to the farm, stopped over a plump helmet, and immediately decided that even "No Job" was preferable to surviving the upcoming winter, wandering off to do nothing and leaving the plump helmet in my farm plot.
If it's a bug, then it's definitely something Toady should look into; if it's not a bug, it's still something I can't figure out how to fix and I'd appreciate any help, as I was just starting to get attached to this fort. Save uploaded here: http://rapidshare.com/files/71406232/save.zip.html
Also, on an unrelated note, kobold thieves appear on the unit list before your dwarves know that they're there. I happened to check the unit list a while back and see a kobold on it. Puzzled, I waited a couple of moments, expecting a kobold thief and wondering where it would appear, only for it to pop up right next to the closest thing I had to a military dwarf.
Version is 33b, newly generated world.
[ November 21, 2007: Message edited by: Gelmax ]