The config.xml file has an error.
To get rid of the error, you can remove all the comments in the file that precede the <?xml code. The <?xml line must be the first line in the file.
I tested this by loading config.xml on my server and then removing the comments and refreshing - that can be viewed with the browser. If you view it before making the change, you'll see the error.
The gallery xml looks good, and it's being called with cache disabling code, which means the cache is not the issue. You should remove any cache related changes, although they probably aren't doing any harm.