i can't duplicate what you're saying.. and i guess i'm not entirely clear on how you're working.
it's possible you have a corrupt file somewhere but before i start recommended resetting them, i'd like to know what happens if you do this:
menu -> Restart...
make sure the box "Reopen windows when logging back in" is unchecked..
click 'Restart'
let the computer boot back up and launch SketchUp..
what happens?
do all the recent files open or is there only a single blank document which opens?