My pentax 16-45mm cannot focus in my K10D!!! Please help~~

[yuen]

Hi, I just bought a second hand pentax 16-45 lens...when I put it to my K10D, it simply cannot focus at any point at 16mm!!

My K10D has no problem in focusing when using FA50...

and when I put the 16-45 into K-m, it works perfectly well...

Is it my 10D's problem? I have never updated the firmware stuff...

or is it the 16-45's problem?

Please help me~~~~