Ether bars can be imported in my fortress. Might want to get that fixed.
Interesting. This seems to be a problem originating from the new reaction. Apparently, dwarves will never melt down objects on their own (which is why they weren't carrying them in all previous versions), but this new reaction gives them a non-melting way to obtain them - even though it's functionally identical.
What I'm going to do here is replace the "melt ethereal spheres" reaction with a "prepare ethereal spheres" reaction, which will take one ethereal sphere and produce one ethereal sphere. Regular ethereal spheres can be melted normally, while masterwork ones can be put through this reaction to create non-masterwork ones without causing a tantrum spiral.
That way, if you're having problems with masterwork ethereal spheres, melt all of the regular ones and then put the masterwork ones through this reaction to make them lower quality (by deleting them and replacing them with another one - custom reactions that consume masterwork items do not cause tantrums) before melting them as well. This reaction will no longer require fuel, but will still be found at the smelter. Expect this change for 0.14b.
If you're impatient (like I would be), here are the reaction raws.
(found near the bottom)
Replace the entry for REACTION:ETHER_SPHERE_MELT with the following...
[REACTION:ETHER_SPHERE_MELT]
[NAME:prepare ethereal spheres for melting]
[BUILDING:SMELTER:NONE]
[REAGENT:A:1:TOY:ITEM_TOY_ETHER:INORGANIC:ETHER_METAL]
[PRODUCT:100:1:TOY:ITEM_TOY_ETHER:INORGANIC:ETHER_METAL]
[SKILL:POTASH_MAKING]