I can confirm that this bug exists in Karmic's version of arpwatch as well. Steps to reproduce:
1) start arpwatch running (or install it, it's started automatically if you do)
2) disable networking to your PC via the NetworkManager applet and re-enable it
3) check top, arpwatch is now using up 100% CPU in the background and continues to do so until restarted
I can confirm that this bug exists in Karmic's version of arpwatch as well. Steps to reproduce:
1) start arpwatch running (or install it, it's started automatically if you do)
2) disable networking to your PC via the NetworkManager applet and re-enable it
3) check top, arpwatch is now using up 100% CPU in the background and continues to do so until restarted