(Solved) Uno not turning on

Development Tools IDE 1.x
1

So, I plugged my Arduino Uno in this morning but it didn't turn on. It worked just fine last night. What happened?

2

I see that you apparently solved it. How about writing how you solved it, so it can be of help for other newbies facing the same problem?

// Per.

3

So, I plugged my Arduino Uno in this morning but it didn't turn on. It worked just fine last night. What happened?

What happened?