Today we used the clickers with a quiz that Chris was giving in the classroom. Putting it midly, it didn't go well! We were not able to get the clickers to work at all at first. Since we only have one set, earlier in the week we had moved the clickers AND THE RECEIVER to another classroom to use it in there. Once we brought it back into the 5th grade room Chris plugged it into a different USB port on the computer. Because teachers do not have admin access to their machines (for different security reasons), the receiver did not get fully setup and would not pick up the clickers when the students started clicking (or at least that is my best guess at what happened). Once I pulled it out of that plug and put it back into the same port as when I installed it (with admin rights) they seemed to work again. Of course, by the time I figured this out after various troubleshooting efforts, we were 15 minutes into the period and Chris had to go back to paper and pencil so she could get through the assignment.
It was user error that was the problem, but I wanted to share what may be a common problem/scenario in classrooms.