For anyone trying to use Hair simulation, and are getting the Access Violation error which is not allowing you to simulate any hair, this is possibly due to the Cloth simulation parameter Self Collision as stated by VirtualWorldDynamics above.

They both share this parameter setting, but it is not available for Hair dynamics (greyed-out). The issue lies with going from cloth simulation using self-collision, and then moving on to hair simulation (even if at a different time, or day). This is due to the INI saved state file which records, and presents the last used parameters. If self-collision was last used on a cloth simulation, then it is locked in, and when using Hair simulation you will notice the greyed-out checkbox is indeed checked when it should be unchecked. This is causing the access violation errors.

Gérald is working to rectify this for the next version (as stated above), but for now, a work-around is to before you select your Hair mesh and press the Hair button, open up the Dynamics Parameters Tab and uncheck the Self Collision checkbox. Then select your hair mesh and press the Hair button. You will see the greyed-out checkbox is now clear. Your hair simulation should now work as expected.

I hope this helps...