Sometimes when I use Alt-Tab (Windows keyboard shortcut) away from firefox, I will be sent back a page as though I had pressed the back button.

Never had that problem. Alt+Tab should be going through the Windows Task Bar to switch between windows -- it is not uncommon to have more than one Firefox Window open. On your Windows 7 you should see an array of you open windows and be able to identify them from thumbnails and see if you do have more than one Firefox windows open. Assuming that something is actually wrong do you have the same problem in a panoramic type of view with WinKey + Tab.

You can create a new window in Firefox with "Ctrl+N" and also in many other applications. In Firefox you may drag a tab to bookmark or reposition and instead accidentally carry it below the tabs bar causing tab tearing which creates a new Firefox window.

Ctrl+TAB in Firefox works in a similar fashion and goes through tabs to the right or Ctrl+Shift+Tab going to the left, both will wrap around to restart The windows keyboard shortcuts do the same.

Once you solve your problem, don't forget to return with the solution, and to mark one answer that will best help others with a similar problems. But don't be rushed, especially on something that is hard to duplicate.

No, I do not have the same problem when I hit the windows tab key. Using this I found that by simply pressing the Alt key I will be sent back a page as well. If I hold down the Alt key I will continue to go back at about one page/sec.