I'm pretty sure I've broken the internet. Why is this so slow?

What's happening: I've followed the instructions to the letter, even tried copying and pasting the necessary sections of the final project into my work and some how it's completely crashing the site!

The site I'm working on currently has two very simple pages 1) Home page with two paragraphs of text and an image, and 2) Contact page containing a form identical to the tutorial (although, not in a table). In other words, not at all heavy.

I start from a clean slate - deleting all files from the sever before re-uploading. First time i go onto the site - it's a dream. Very quick to load etc.. As soon as i submit a contact form, all hell breaks loose!

1) I never reach the header ( 'contact?status=thanks' ) page. ALTHOUGH, I do receive an email as expected, and the destination does change in the address bar. It's always loading but never loads. 2) The site starts a never-ending download e.g. (firefox) loading wheel never stops turning on either of the pages. 3) Site becomes slow or totally unresponsive on multiple devices. 4) Closing browser completely and re-entering the page doesn't help - doesn't load or has never-ending download. 5) Another site I have on with the same company (123-reg) also becomes very slow at the exact time this website breaks. Have I broken the internet? Maybe this is just a coincidence.

Any help would be much appreciated.

Would using SMTP avoid this problem? If so, would I include the smtp.phpmailer file instead of the class.phpmailer file? The tutorial on the blog post (http://blog.teamtreehouse.com/sending-email-with-phpmailer-and-smtp) doesn't show an inclusion of the file via the contact.php page, just that it sits on the server.

T