Thanks for the report!
Most probably your database is corrupted. Please export it to XML, create a new notebook, and import the XML into it. After that deleting a tab will become possible.

About not remembering position: please report in a separate ticket. Thanks!

Chris, for IE there seems to be a workaround: try turning on Print Background Colors and Images under options on the print preview.

Indeed :) Thanks, Chris!

Thanks, Patrick!

Great!

Ok great. I'll merge this issue and that one to unify votes - this way this will get implemented sooner

You can try another color theme from the View menu. It influences the color of the tag sidebar and search filter backgrounds (but also the main icon color, so probably you should try "Cyan")