I have a Nikon f55 digital camera - could I use the lenses on the Nikon d40-x?

I am interested in buying the digital slr but wondered whether i could save some money by only buying the standard lens model.

Your current lenses will FIT on the D40x but chances are, they won't auto-focus or meter. Only Nikon's AF-S and AF-I lenses work properly on the D40 and D40x. Your lenses will work like a charm on any other Nikon dSLR though.
Perhaps get a 10 megapixel D80 or look for an old 6 megapixel D50 or D70. (The D80 is a much nicer camera in many ways, but 6 megapixels is plenty for a full page print.)
Another thing to consider, is that all of Nikon's dSLR models magnify lenses by a factor 1.5. So if you slap a 50mm lens on a D80, it will seem to be a 50mm x 1.5= 75mm lens.

I don not know the answer to your question but can make a suggestion if you check on www.cnet.com they review all digital cameras and usually answer those types of questions in their review. It can be a very helpful site when researching a digital camera to purchase. I was recently looking for a new small pocket size point and shoot camera and found there site very informative.

If it's an auto focus lens the meter will work but only AF-S and AF-I will auto focus with the camera.

All the lenses you have for your F55 will work on almost any D series camera from Nikon. The D40x will only auto-focus with AF-S and AF-I lenses. If you have auto-focus Nikon lenses other than those you may want to choose the Nikon D80.