Windows 7 - Backup and restore failure with error 0x80070020

I have a Dell Inspiron N7010 laptop (64 bit) with Windows 7 operating system.  I have had it since Aug 2010 and had no problems backing up using Windows Backup and Restore until April this year.  Suddenly I got error code 0x80070020 and message saying backup did not succeed.  I tried all sorts of solutions which did not work until this one...

• Change Windows Backup and Restore settings by clicking on the user and show files, then uncheck the AppData Folder.  I  was able to run my backup successfully but because this folder was not backed up it is only about half the size of previous backups.  Then about a month later Adobe updated my Flash Player so I tried the backup again with the standard setting letting Windows choose and it worked and is still working.

HOWEVER, I NOW HAVE TWO MORE PROBLEMS....

1. I also have a Dell XPS L701X laptop (64 bit) with Windows 7 operating system which I have had since Feb this year which has been running fine until last month (October 2011) when the Internet Explorer (v9) occasionally stopped working.  About the 11th November I had a lot of updates on Windows Update and also Adobe Flash Player updated to v 11.1.102.55 which included ASK toolbar.  My next backup failed!!!  So, I have tried the following...

• Uninstalled ASK toolbar and tried backup - it failed.  Did not restore the toolbar.
• Uninstalled Adobe Flash Player and tried backup - it failed.  Reinstalled Adobe Flash Player.
• Tried all the automated troubleshooters and problem testers without any sucess.
• Ran backup without backing up AppData folder and it works - but AppData folder is not backup up!

• I have a printer (HP Photosmart C4780 wireless) which I use for both laptops and have no problems except that on the XPS laptop I have a message saying there are no drivers for it.  I have uninstalled and reinstalled the printer several times and the drivers are definitely there, and it is working fine.  How do I get rid of the erorr message saying I have missing driver?

 I would appreciate any ideas!