I know this is digging up an old thread, but at least it's mine to dig up!
After having the issue of the sketchup.exe process not unloading since the original post, the issue seems to have resolved itself. What I did was to update/install several of Chris's plugins (of the "Chris Fullmer Tools" variety) that I had installed, and the Kerkythea exporter. I'm not sure which one of these scripts/plugins caused the issue if any, but if anybody else is having the issue and has some of these installed, they may want to try updating their files as well. Absolutely no other system changes were made (Windows updates, etc...). Using SU version 7.0.10247.
Files changed:
SU2KT
component stringer *
perpendicular face tools *
Greeble 2
3 line tools *
Scale & rotate multiple *
Select outer edges *
Components onto faces *
new install, the rest were updates.