Up until a couple months ago, Windows and Linux interfaced just fine. I bought a faster Netgear router and I thought maybe that was the problem. But I just hooked up an ASUS router and I still have the same problem.
If the usb drive plugged into the router can not be seen by your linux machine, but is seen by the windows machines, you do not have a windows sharing problem, you have a network problem with (most likely) the linux machine, or the router setup with the linux machine.
The sharing problem between the windows machines and the linux machine is a side effect of the linux machine network problem.
Until the linux machine can see the files on the router usb drive, troubleshooting the windows sharing is downstream of the problem because the router-linux box network problem needs to be solved first.
When the linux box can see the files on the usb drive, your windows sharing problem will be solved at the same time.