The nether ores mod is generating 'bad' ores that won't smelt into their regular counterparts.
135:0 (nether coal) through 135:7 (nether tin) will all smelt normally, but anything higher like 135:8, 12, and 14 will not smelt. They're all called "Nether Tin Ore" and appear to be duplicates of other ores (8 is an unsmeltable nether coal, 9 is an unsmeltable nether diamond). Using /item I can even get stuff like 135:1000, another unsmeltable nether coal.