i have 2 here and both seem to fine, even after one got hot and i thought i killed it.
any chance of posting the code you are using, heres a copy of a file i used to constantly increase image distance, and asked the FPU to read back the new answer, and worked fine for more than 10mins.
it maybe helpful if you try the code in the the pdf i posted, it works fine, altho when copied and pasted to the editor the formating is kinda funky.
it is worth noting that things like the FPU reset routine need to be run before you can start using it, along with the pause 10 after a sum to give it chance to finish.
however the most frustrating thing that was left out of the maker data sheet was the fact you have to point to the correct registery before reading back the data, i have not yet figured out, negatives and readbyte and alikes, i normally just use read float (fyi, when you load i have been getting results only after i added the fset0 to the initial loading of data)