Setup and Hold time VS temperature (and temperature inversion)
The 'temperature inversion' you are talking about is not happening at 90nm as far as I know. However if you operate a circuit in subthreshold you will see that effect.

If you know it is either a setup or hold failure then to distinguish between a setup and hold failure the easisest way is probably to reduce the clock frequency. 

If the error corrects itself at a low frequency then it is probably a setup failure. If however the error is impossible to correct it was a hold failure. 

Note that reducing the clock frequency reduces self-heating, so you might have to tune up the ambient temperature a little bit.