You can try this:

Open Device Manager and expand list under USB. Then double-click on a USB root hub. Click Power Management tab and UNcheck the box "Allow PC to turn off...". Click OK back to Device Manager and repeat for all root hubs.

Then expand list under Human Interface Devices and look for a Power Management tab for each HID entry. Uncheck the boxes "Allow PC to turn off..".

Exit Device Manager when done and reboot. See if that solves the problem.

Hi RoHe. Short answer - I did. It didn't. If you've got any other suggestions, I'd like to try 'em.

What system effects occur by removing and replacing the wireless adapter? That's the only thing it takes to get back to work. Shutting down or restarting will also do it, but removing and replacing the wireless adapter is a lot quicker, but it'd be even quicker to not have to do that. Thanks. 

It's usually something to do with power settings. So the other place you need to look is in your Power options in Windows.

For example, Selective Suspend could be causing your problem.

OK, thanks RoHe. After reading the link you provided, http://www.sevenforums.com/tutorials/147369-usb-selective-suspend-turn-off.html?s=4a15f3ec09c206e7b71c099c607316f3, it looks like I want Selective Suspend enabled. I checked and that's what I've got. I went down the Device Manager and checked all the don't turn off, and allow to wake up boxes that I could. Same behavior. Bummer. Any other ideas?

what is it that removing and replacing the wireless adapter does? What setting or registry edit will ensure that happens without physically removing and replacing. Thanks.

Disconnecting and reconnecting the dongle forces the PC to see that a  new USB device is connected, just like when you connect any other USB device.

I think you want Selective Suspend disabled.

You may also want to disable Hybrid Sleep.

And if this K+M uses its own specific driver (vs. a generic Windows driver), see if there's a new update for the driver.

BTW: Are you connecting the dongle to a rear USB port, and have you tried different rear USB ports?

Disconnecting and reconnecting the dongle forces the PC to see that a  new USB device is connected, just like when you connect any other USB device.---So, how can I tell the computer that the K&M are always plugged in? I think you want Selective Suspend disabled.-- OK, made that change. You may also want to disable Hybrid Sleep. -- OK, made that change too. And if this K+M uses its own specific driver (vs. a generic Windows driver), see if there's a new update for the driver. -- Apparently no Dell driver. BTW: Are you connecting the dongle to a rear USB port, and have you tried different rear USB ports? -- For the first couple of weeks I was using a rear USB port (as I always had), but because that makes it so inaccessible, I've plugged a powered 4-port USB hub into the same port that the wireless adapter was previously plugged into. This lets me remove and replace easily relative to getting to the adapter plugged into the back.

OK, I'll make that change tonight before I go to bed. I'll let you know tomorrow if anything changes.

Yes, but...

Now that you've made all those changes, have you tried connecting the dongle directly to a rear port? The PC is seeing the hub so it doesn't know Human Interface Devices connected via the hub and may turn the hub off.

Well, Darn. I was optimistic, but no change in behavior. The reason I was optimistic was that when I moved the wireless adapter to the back of the computer, I got a window saying that a new device was found and drivers were being installed. I took that as good news, but...................:emotion-6:

I'm not sure if there is a default setting for your Keyboard and mouse. I'd do that and get the USB extender

works great for me on my DT 755 line of site is always better.  And I know this is a Dell site go with the LOGITECH K800 and at least a x mouse.

Best of luck