Got a crash using fastcraft-1.22-ctest22.jar.
Was connecting to a dedicated server running the same version, immediately after updating both from ctest21.
The actual crash begins on line 8179 and appears to be an issue with Thermal Dynamics server when it is accessing a neighboring block that has changed states.
Will try rolling back FastCraft version.
Edit: Changing client back to ctest21 fixes the issue or at least allows me to play without crashing.