Bad Beginnings

Lately, I've been having a problem with beginnings.

Usually, the beginning is the best part of anything that I write. It gets a little sloppy in the middle. The ending is quick and sharp. Since I started seriously writing novels all of the way through, my general theory has been that my middle was my problem. I spent the most time on it because that was what needed the most work. I plowed through the beginning while I still had tons of steam and plowed through the ending when I got my second wind.

Like I said, this is not the case anymore. I have had two really good ideas for "serious" YA's. I set to work on the first one right away, ready to use up that creative energy that had been building behind the idea only to flop. 2000 words in and I hated it. I thought that I hadn't developed the characters enough in my head so I spent a day writing everything I knew about each character. That went well enough. I attempted writing again and FLOP. I hated it. I couldn't see how to get where I wanted from where I was.

Today, I spent a little time writing on my other idea, thinking this would go better. FLOP. Maybe I should keep writing then come back and fix it? Maybe I can write it then chop it up?

Does anyone else have a problem with bad beginnings? What is part of a story is easiest for you to write?