Backspace and arrow keys not working as expected

This seems to happen to me when I open a solution and there are files already open. I used to close the files, then close and re-open the solution to fix it, but now I just hit Alt + Enter.

Here is the blog where I found this trick.

i'm still seeing this issue even after the ALT + ENTER.

However i did notice if i had more than one window open if i clicked into each file then attempted backspace, eventually it worked on one, and then I seemed back in a working state.

I also found this is to be the case when a modal dialog is present, even if it is not visible. You might check if VS has some alert dialogs in the background. Closing them returns to normal state.