I recently tried to use EasyTether on my development machine with disastrous results!
It didn't really work well and when I went back to developing adb could not see my devices anymore!
the adb devices command would display nothing!
After a few hours of searching around I came across this stackoverflow post that helped me fix my problem.
Here's the things that I did to troubleshoot:
1. rebooted the phone and machine
2. removed the network connection created by easytether
3. checked the usb ports and cable
4. made sure USB debugging was checked off.
5. unplugged and plugged in several times
6. repeated steps 4 and 5 on other devices.
Once I had gotten no results I knew something else was going on.
Some sleuthing yielded the thread on stackoverflow. Did I mention I love stackoverflow?