This is an issue that I encounter very often when programming with ADT on Eclipse.
In short, there seems to be a couple tasks that are waiting for another task to complete which is blocked. It doesn’t matter how many times you restart Eclipse or restart your computer, Eclipse will still be in this situation, preventing any work to happen.
After doing some research on Stack Overflow, I figured there were 2 effective solutions to this problem and 1 other solution that is less optimal:
Launch Eclipse with the clean flag
This is what should be tried first. After running this command, Eclipse will open in a special cleaning mode which should cancel all those hanging tasks.
Create a new workspace
Another way to solve this problem is to recreate your workspace from scratch.
Delete the .metadata folder in your workspace
Finally, and this is the less preferable solution, you could remove the .metadata folder all together in your workspace (note: this is a hidden folder).
Keeping this as a memo to my self in case I encounter this again, as well as to help anyone facing the same problem.