We've had squeeky floors for years, we tried to fix the squeeks with screwing down the floors into the floor joists but found that we still had a few spots that still squeeked. After close inspection we found that when the builders put down the subfloor, in some areas they did not lay the subfloor correctly, meaning tung to groove. They instead layed the subfloor down with two cut edges causing the plywood to rub as you walked over it.
We thought that maybe we could somehow screw the two sheets of plywood together which lead us to thinking that if only we could staple the two sheets together that that might work. We remembered the giant staples we used when installing our electrical wiring. So, what we did was take the large electrical wire staples, cut the side flanges off with a saw and hammered the staples into the floor joining the two sheets of plywood together. Well it worked. I wanted to pass this on to all those who are pulling thier hair out trying to come up with a fix.
If you come up with a great fix, pass it on.