I have a fort in 40d that seems to be suffering from the same or a related issue.
The fort has a magma pipe, and I used to be able to build magma workshops.
Then there was an unfortunate incident involving a fisherdwarf and a fire imp. Additional casualties were incurred while attempting to retrieve the body, and before you know it, I had a child turn a potash maker into a boot, a captain of the guard with a 201-day prison sentence for murder, and a berserk mother killing her baby, only to be promptly dismembered by her obsidian-sword-wielding husband.
Everyone died.
Just to add insult to injury, a goblin ambush waltzed in just as the crazy stonecrafter was killing off the last, bedridden mayor, and claimed all the credit: "In the early winter of 125, The Wraith of Wetting defeated The Net of Feeding of The Escorted Bridge and destroyed Rootermachines.".
I reclaimed the fort, and now am
not able to build magma workshops.
This is very unfortunate, because I tore down my only magma smelter to make room for a pump as part of my move-all-of-the-booze-and-beds-into-the-basement-and-then-flood-it-with-magma plan, when it became clear that the existing justice system was simply not keeping up with the tantrum spiral, especially since the metalcrafter and all of the masons were rioting, bringing the production of much-needed chains and coffins to a grinding halt.
Before-and-after saves here:
http://dffd.wimbli.com/file.php?id=720That includes the last seasonal save before the fort initially succumbed to fun, where magma workshops are buildable, and the first seasonal save on the reclaim, where they're not.