Why are some of the edit buttons on some questions active and others not?
The reason for "edit" link disabled are-
- A large number of suggested edits by you were rejected in the last day. You are banned for a week.
- We are out of empty slots in the queue.
- There is an edit to a particular post that was not approved yet.
- You are not logged on and the post is less than 10 minutes old.
For full summary read here.
For your case it appears to be the second point.