Share 'Sharing "DOH!" moments.'

I thought I would start this thread share some "Doh!" moments. For myself, I was writing about an hours worth of code and forgot to follow the golden rule of incremental development. So after about 3 hours I ran my code and ran into errors. Went to the lines that had errors and my syntax was correct. 30 minutes later of looking at the code I came down to a simple indentation error. "DOH!"