MC 1.7.10 // Forge 1208 // Mekanism 7.1.0.89
Mod List --> https://docs.google.com/spreadsheet/ccc?key=0ApCkT7oXxGE4dGNRNTRfbTBhYVNDVllubDM2UThpRlE#gid=0

I ran into trouble today while trying to use Mekanism's Copper Ingots in the Crucible from Flaxbeard's Steam Power (v0.26.1). The Crucible from FSP would not accept the Copper Ingot from Mekanism at all, refusing to melt it down for blending with zinc in an effort to make brass. I checked the Copper Ingots from FSP and those worked fine.. so initially I thought that FSP was to blame. Further testing revealed that Mekanism Copper Ingots would work FINE in the Alloy Smelter from Ender IO, for any custom recipe called for "ingotCopper". This further strengthened the case against FSP.

Then I decided, based upon the suggestion of another user in IRC, to change the load order of the mods. I forced FSP to load LAST, after Mekanism (as FSP normally loads BEFORE Mekanism). Suddenly.. this magically resolved the issue. Mekanism copper ingots work just fine in the FSP Crucible. After revealing this to others in IRC, the comment was made that if Mekanism doesn't load before Tinkers' Construct, that mod has the same kind of issue with Mekanism Ingots.

So .. it looks like Mekanism is doing something strange with ingot registrations, if it loads AFTER other mods that use those resources. I don't -fully- understand all of this, so if you have further questions I will try to be the best help I can.. however I might not be able to provide much more in terms of details.

Going to close, I provided a detailed description of my interpretation of the issue in IRC if you want it to report it to the FSP developers.