I found the answer, and I'm pretty certain you don't need to see any more code!
Above I posted:
RewriteRule ^$ http://www.domain.com/
...and said it was telling me there was an infinite loop.
It baffled me to start, but I'm sure I've figured it out now.
That line of code redirects domain.com to domain.com. No wonder it came up with the error.
Why do you need to see more code?