SX280 HS no longer recognized as connected to any computer/ device

Question

I purchased the brand new PowerShot SX280 HS three weeks ago. Being a person that actually reads directions and owners manuals, I followed the Getting Started booklet exactly as stated to connect the camera to my Win 7 (64-bit) PC, and it worked well to automatically transfer my photos to the computer via USB cord using CameraWindow. 
Within a few days, I had also set up the camera's wifi connection to the same computer, and it worked fine to transfer selected photos to the computer.  I *think* that I could still also connect to the computer via USB at that time.  I also set up wifi connections to various email addresses and to Canon's iMAGE Gateway online.  However, I was never able to connect via wifi to my tablet (Motorola XOOM, Android 4.1.2) 
A few days later we took a week-long trip out of town for our dd's college graduation (the whole reason for the camera upgrade). Rather than waiting a week to download the photos to the home computer, we tried to connect the SX280  to our Win 7 (32-bit) laptop via USB, having previously installed the Canon software. However, the laptop would never recognize being connected to the camera.  After trying the set-up several times, we finally succumbed to using ImageBrowser to import the pictures directly from the SD card inserted into the laptop. 
Upon returning home, I wanted to download the pictures to the home PC, but now had the same problem as with the laptop: CameraWindow, ImageBrowser, and Windows Explorer all gave me the same error - no camera detected!  Tried using ImageBrowser to import the pictures from the SD card inserted into the PC, but even that was not recognized by the computer! Finally got the computer to "see" the SD card when I put it into a USB card reader and connected that way. Whew!
Tried again today to connect the camera to the home PC, but still no recognition by the computer of there being a camera connected via USB.  In an attempt to start over from the beginning to connect the camera to the computer, I resorted to removing that computer from the camera's wifi settings, deleted the camera profile from the computer's list of devices, and removed all the Canon software from the computer, Alas, during the software installation process, when the time came to connect the camera via USB to the computer, I received the same error - could not detect any camera as connected to the computer!  
Did setting up the wifi connections somehow disable the ability to connect via USB? 
What to do???  There is now a big Firmware Update available for this camera to correct a major glitch, but I fear I will not be able to install the update if the computer cannot detect the camera.

Answer 1

When using other imaging devices with your computer, the conflict between the two (or more) devices and software may corrupt the camera driver, which is provided by Windows.
You've already done some of this, so I apologize, in advance, but I'm going to ask you to go back to the Device Manager.
Before you go:  If your computer is a desktop unit, is the USB cord plugged into the back of the computer? (Recommended) If it's a laptop, is your computer running on AC power? (recommended)
Now, on to the Device Manager:
1.  Click on the Windows Icon (used to be the "Start" button.
2.  Click on Computer.
3.  Click on System Properties.
4.  Click on Device Manager and expand "Portable Devices".
Now, while keeping an eye on the Device Manager, connect your camera and power it on in the playback mode.
If you see the camera driver appear, please right-click on it, then choose "Delete".  Next, turn the camera off for a few seconds (10 or so), then turn the camera back on.
What happens?
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