You may have accidentally removed the task bar applet from the panel.
Try right clicking on the panel then Add/Remove Panel Items. Check that Task Bar (Window List) is shown on the list. If not press Add to re-add it and up/down to put it in the right place. Also tick the box in the stretch column so it fills all available space
Are you sure the upgrade went though successfully? Try running sudo apt-get upgrade and sudo apt-get -f install and make sure they don't report any errors.
Next, I'd check if you can get a USB BT adapter working (if you have one). That would tell you where to look next.
If none of your adapters work, you're likely having trouble with the BT software stack. ...