Character Motor Script Corrupted

So my game has started crashing on loading a game play level ever since i updated to the 4.1.3 version. After many different tests and long frustrated hours on debugging I isolated the problem to disabling the character motor script (provided by unity in standard assets) and it started to work. Unfortunately the character motor script is essential so i cant think of a work around. Am i going to have to re-install an older version of unity?

Re did the motor script in C#, renamed the script, class, and all reference calls in other scripts
Was a pain but works