Beginning to ask a question on Stack Overflow actually helps me debug my problem myself, especially while trying to formulate a coherent and detailed enough question body in order to get decent answers.
Is this common?
This technique is known as Rubber Duck Debugging -
The process is to meticulously explain code to an inanimate object, such as a rubber duck. It is expected that when the programmer comes across a piece of code that is incorrect, she will realize this.
Often times this will happen when I'm preparing to ask a question on SO. My question will be far too specific to my code, so I'll be working out how to generalize it. More often than not, the process of generalizing a problem makes me aware of a mistake or design flaw in my "real" code, and hence solves my problem.