NOTE: There is a crank-spindle interface called "power spline" that uses a spline spindle. The crank bolt is an 8mm thread. Because the hole in the spindle is small, use the CCP-22 or CWP-7 for this crank, the same tools for a square spindle.

From here:http://www.parktool.com/repair/readhowto.asp?id=120

I don't know if this is the situation, but older Specialized OEM cranks used this "power spline". It should say somewhere on the crank if it hasn't rubbed off already. This was very annoying when I first found this out.