I had this a few days ago, but mine seemed to be closely related to the caverns, so it's probably not what the OP is seeing since he says he hasn't hit his caverns.
I normally seal off the caverns once I reach them, but this time i had reopened the cavern to build a minecart track down through a bit. Some time after reopening the cavern I started getting massive spam from hunters unable to path to their prey, and weavers unable to path to silk to be collected. This was despite the fact that there was plenty of silk close to the spot where I had a passage into the cavern. I think what was happening is that they were selecting prey/silk in an area of the cavern that they couldn't actually get to. Once I built a few walls to seal off the cart tracks from the rest of the cavern, the cancellations stopped.
So for some reason the job selection code though they could path through the cavern to the prey/silk, so it assigned the job, but the pathfinding algorithm couldn't find a path. maybe it just involved a path that was too long and convoluted for the pathfinding algorithm.
Also, you can mass forbid *everything* by doing d-b-f, then going to the top left corner highest level of your embark and hitting enter, then go to the bottom right corner of the lowest level of your embark and hit enter again. that should forbid everything in your fort. Of course, this will result in more cancellations, so you'll then need to figure out a way to un-forbid everything that you actually want to use. Maybe through creative use of the stockpiles menu.
Another option is to go into the stockpile menu and start at the top and forbid all of one type of thing, see if the spam stops, unforbid them, then forbid the next type, and so on. For instance, start with forbidding all of the various meat, exit the menu and see if you're still getting spammed. If so, go back and unforbid all of the meat and forbid all of the fish. Eventually you'll find out what type of item is the culprit, then you can just go back and forbid the first half of that type and see if the bad item is one of them, and so forth narrowing down until you find the item that is causing the problem. It'll probably take a while, but it will work.