D90 not compatible with "older" lenses?

Hi, I just bought my brand new nikon D90 and have been trying it out with my old former Nikon 70-300 mm, 4,5-6 G lens and with an also old Sigma 24-70 mm 3,5-5,6 D lens. nearly a 90% of the pictures are not really sharp or clearly blurred much as at the time of shooting the image looks crispy in the viewfinder.I have tried all the diferent types of focus modes in the D90. Anybody knows if that is due that this lenses are not DX lenses or may be too old in manufacture?
thanks for any hint and help!
Joan

It doesn't matter that they are not DX lenses, and they are not too old. There are many things that could cause blurred images. What shutter speed(s) were you using, and were you using a tripod for your tests? Put the camera/lens on a tripod, use a fast shutter speed, and focus manually and see what you get.

Thanks for your comment, Alan, well one thing is that have been using f stop numbers which may be are to big, f5,6, the results are better at f11 or more, but even so at least one part of the insect for example should be sharp, the shutterspeeds were high enough. The thing is that the same type of photos came out OK with the same lenses on my F90X--

Well Hans, you should actually be getting more DOF with the D90 due to the smaller-than-35mm sensor. Although I'm not familiar with macro focusing (you mentioned insects) so things change a little at minimum focus distances. I would definitely follow Alans advice and do some simple tests to eliminate variables. Tripod, high shutter speed, manual focus. If that works then it's possible that the autofocus is miscalibrated. So then try tripod, high shutter speed, autofocus. If that works, then you've probably just got some sort of motion or vibration blur.

Hans I use the D90 as a second body and have no problem with older lenses.
Check the back glass on the lenses for dust or fingerprints.Just a suggestion.
AVI