I am using google webmaster tools on my blog, and it keeps showing me two URLs that can't be found, and I can't find out if one of them is from wordpress. The first is http://guitarfact.com/category/uncategorized/, which is pretty easy to fix. i just need to create an uncategorized category correct? The second is harder; http://guitarfact.com/function.require, I'm not sure how to fix this one.
Run Xenu across your site and then look at the info for the links. I suspect google probably indexed while you were tweaking your theme and found the function.require page. I wouldn't stress over a few broken links in it's reporting. I would resolve some of the other issues that Xenu has highlighted though: 6 pages timeout and you have your http://guitarfact.com/ and http://www.guitarfact.com/ mixed up.
There's a cool tutorial on Blog Storm explaining how to track the referring pages for 404 errors using Google Analytics http://www.blogstorm.co.uk/blog/advanced-google-analytics/