syntax error, unexpected ':'

[khamseen]

Disregard. I forgot to update my main sites PHP system to 5.5 instead of 5.2... Rookie error.

[Shambles]

It's poor form to erase the content of your message... your issue & resolution may have helped another member.

[khamseen]

Well I didn't think it would matter to anybody else, but since it might I'll add what the issue was here as I can no longer edit my OP.

I'd been working on a modded version of the default theme for a few weeks. It was all running great on my test server but when I pushed it out to my live server I kept getting the error named in the title.
The files were identical on both servers so it made no sense to me why I was getting the error. Then I remembered that I had my main server limited to PHP 5.2 because I had been running some outdated stuff until recently. And as soon as I remembered that I realised that's why it wasn't working as I'd used shorthand ternary operators which were added in 5.3. Switching my server to 5.5 fixed it...