Blue Connection Bars?
 

What does it mean when the connection bars in the bottom left-hand corner of the screen turn bright blue instead of green? Does this have anything to do with why sometime limewire won't close when I try to exit the system?

Blue bars indicate a turbocharged connection...that's a very good connection:)

How do you have LW set to close within options (tools > options > system tray)? If you have it set to shutdown after transfers, LW won't close until all downloads & uploads in progress have finished. Maybe that's what's happening to you sometimes?

Thanks! I'll check my options and see if that's the problem with it shutting down. Sometimes it locks up right as it's verifying a files contents...not sure what to do about that.

If they are a dark blue then its in a state of hibernation. Light Blue signifies a Pro connection or user.

AFAIK it's still possible to get a turbo connection with basic...if you're connected as an ultrapeer. I used to see turbo occasionally when I used basic (that was ages ago).