One page in site slow

I’m having trouble with one page on my site. It’ll work fine for a couple of refreshes (less than a second to load), then either after a couple, or when i change anything on it it just doesn’t load. Firefox tab has the Loading text on it, the status bar says Done, and thats all it does.

The page is made up of several (couple of includes & templates)

The page itself

Other pages with incorrect usernames load instantly with the user not found, such as

The php file

with extra functions within the functions_userpage file

the template

Any idea why this page doesn’t load.
The error log gives no help, just a few file not founds to do with images, and not actually having a 404 & robots.txt files, which have been sorted anyway