The English Civil War was a complex beast, with many causes and consequences. One of the main issues was the king's absolute power, which was a bit of a sticking point for the Parliament folks. They wanted to limit his powers, while Charles was all, "No way, I'm the king, hear me roar!"
Another major factor was religion, because, you know, nothing says "let's go to war" like a good old-fashioned theological debate. The king was an Anglican, while many Parliamentarians were Puritans, and they didn't exactly see eye-to-eye on things like church governance and future hats. It was a bit like a schoolyard fight, but with more swords and fewer recess monitors.
And then, of course, there were the economic issues, because who doesn't love a good tax fight? The king wanted to raise taxes without Parliament's approval, which was a major no-no in the eyes of the lawmakers. It was like he was saying, "Hey, I'm the king, and I'll take your money, thank you very much!"
PPT - Absolutism Unit Plan PowerPoint Presentation, free download - ID