Folks, After having this issue on and off for a few weeks, I've found a solution for me (with a dedicated graphics card)
I believe a windows update set my sketchup default graphic driver to the Intel integrated HD which caused all sorts of slowness issues, not just selection tool. I loaded my graphics utility (Nvidia control panel in my case) and forced sketchup to use the Nvidia card. This has worked well and solved all issues I had. Try it and report back on here if it works for you.
You can also find out which card sketchup is using in the window>preferences>openGL settings.