Finder dragging hang / stuck
I would say restart you Mac if you have not done so in a while.
Try repairing the disk and repairing permissions in Disk Utility. 
Next try deleting your Finder preferences. Your looking for a file called: 

com.apple.finder.plist

Note you might want to back this file up before deleting, if you spent a lot of time configuring Finder view, etc and this turns out to not fix the issue. 

This file will be located at /Users/YourUSERname/Library/Preferences/com.apple.finder.plist
Restart and see if it happens anymore.
Try installing Onyx and use it to reset Finder related settings.
Try removing FlexiGlass if you suspect that is causing issues.
Try logging in as another user and see if the issues comes up while logged in as another user.
If all else fails, back up your stuff and reinstall Lion.