HELP !! I think my ZD50mm f2 is fried...

On my E series cameras is not focusing properly...

I've had this lens for a few years, I KNOW it "hunts" when focusing, but most of the time it focuses on the first try, images were always very sharp, in good light it never had any problem focusing..now it is a different story.

I have cleaned the contacts in the lens and in the camera...by the way, the E-620 locks in the focusing point in a flash, when I use the 14-54mm, the 14-42 or the 40-150mm...

When I have the 50mm on the E-620 even the viewfinder is dark..I don't understand that at all, change it to the 14-54mm viewfinder is bright again...

What can I do?

Thanks in advance

Carlos