Ah ... couldn't for the life of me work out why that change was messing up PHP ... guess what - it wasn't. Sorry, I was pushing the threshold of my patience last night after 2 system installs & crap loads of problems.
My problem wasn't PHP, no, it was the MySQL password. For some reason it was reset or something. I just entered it again using mysqladmin and everything's working fine.
The reason my pages weren't displaying was because the majority of my work is database integrated.
Sorry for the trouble & thanks for the help.