Ivo wrote:
This doesn't sound normal.
Temporarily disable Classic Explorer to see if that is related. Basically do the opposite of what's explained here: 
http://classicshell.net/faq/#explorer_toolbarHi,
I did that and the behavior went back to normal, i.e., clicking once on the folder in the navigation pane, did select it. 
I re-enabled the Classic Explorer Bar and ExplorerBHO Class Add-ons and the problem returned. 
The problem can be seen in the picture below, where the folder colour is not dark blue. 
In the other picture, I have double clicked on the 'Windows 7 Upgrade' folder and it has expanded itself, and it also says 'Searching for items...' in the status bar. 
Does this help?
Thanks,