So last night I found I couldn't sleep because my mind kept working on that coding problem. Today, I got a lot of stuff done for work, but as soon as I was done, I stayed in my chair and went back to the coding problem. I've been working on it non-stop since about 6 this evening.
I finally found the bug that was the show stopper. I should have gone to bed before this because I'm so exhausted, but I just couldn't let it go. This is a problem that I've worked on off and on for years and being so close to the solution, I just couldn't let it go.
Now it works. I'm heading to bed for a well-deserved night's sleep. I still have a lot of work ahead of me, but the hard part is done.