D-50 and Tokina AF400AT-A 5.6 Compatability?

[jq]

Just curious about the compatability of this lens to the nikon? I have had it for several years and it worked fine on auto for my Nikon 8008s. But when I tried it last weekend for our whales in the Sacramento river, I got nothing for autofocus. My understanding that all my Nikkor lenses and those for that camera would work with my D-50? Help!!!!

Does anyone know of a specific site to check on? Thanks again.