It is really reproducible in R2010 SP1 and logged as # 1254347. But there is an easy way to accomplish it. Please sketch a circle on the end planar face with radius "0.03-0.001"inch and then create sweep with this circle and helix to cut it, which should work fine.
Thanks,
River
Thanks,
River Cai
Inventor Quality Assurance Team
Autodesk, Inc.
Email: River-Yijiang.Cai@autodesk.com