Solid Hardwood, Engineered and Laminate Flooring - Having a problem levelling ply subfloor for hardwood

I'm having a difficult time levelling a section of ply subfloor in my house for a 3/4" hardwood installation. I believe there is a slightly bowed joist underneith the affected area, as there is a rise that extends along a particular joist. I would estimate this rise to be close to 3/16" higher than adjacent flooring, with the rise sloping off within about 18 inches on either side.

I just rented a big floor sander and put 20 grit paper on it ($65 for 4 hours...) Spent about 1.5 hours sanding just one small 4 square foot area and have made almost NO progress. Well, there is progress, but it is insanely slow. It would seem I would have to sit the sander on one small path for 4 hours before it would shave off 1/8"...

Is there a better solution? I've pondered the idea of ripping up the subfloor to get at the joists where I can plane or sand those down faster. Or what about making the rise more gradual by putting an extra layer of felt on the areas on the sides of the rise?

This is really causing me some grief.

POST EDITED: Members should demonstrate progressive ideals by avoiding vocabulary considered offensive.

twelvepole

Here are some pics:

The "rise" runs parallel to the level, roughly along the line where the visible wheel of the floor sander is (you can see nail heads along this line):

http://img316.imageshack.us/img316/5616/floorprep11zj.jpg (http://img316.imageshack.us/my.php?image=floorprep11zj.jpg)

This shows the effect the rise is having (left hand side):

http://img316.imageshack.us/img316/5327/floorprep24xs.jpg (http://img316.imageshack.us/my.php?image=floorprep24xs.jpg)

This shows the effect the rise is having (right hand side):

http://img411.imageshack.us/img411/5903/floorprep39rn.jpg (http://img411.imageshack.us/my.php?image=floorprep39rn.jpg)

Another view of the floor (rise perpendicular to the level:

http://img411.imageshack.us/img411/7744/floorprep42gr.jpg (http://img411.imageshack.us/my.php?image=floorprep42gr.jpg)

Members have posted success removing subfloor and using a plane to take the bow out of joists.

I did a bit of research and came to the same conclusion..

So I cut out a chunk of the subfloor (also visible is the half bath floor removed due to water damage):

http://img511.imageshack.us/img511/1044/floorcutout17qx.jpg (http://imageshack.us)

This pic shows the problem fairly well, the cut facing the camera is nearly flush with the door, hopefully this is close enough:

http://img511.imageshack.us/img511/3603/floorcutout25wk.jpg (http://imageshack.us)

As I made the cuts, the edges of the (now removed) subfloor raised up approximately 3/16" higher than the other side of the cut (attached to half exposed joists as seen in images), which is how high the rise appeared to be.

Hope I don't have this kind of problem w/ other areas of the house...