Problem with 50mm F 1.8 autofocusing.

[Alland44]

I just updated my firmware, and my 50mm stopped autofocusing. My cheap 70-300 mm works fine !?

Me being a noob, in digital Slr, wonders if I have made a common error :)

[K1W1]

I doubt whether it's firmware related.

Check that the lens is PROPERLY attached to the camera. Sometimes people do not twist them far enough to fully lock them into position.
Check that the lens is still locked to the minimum aperture position but unlocking and relocking it.

[rawpaw18]

Make sure the f. stop lock is still on.