PHP is now 5.3.3
error log - nothing since 16:22 ( and I've been testing logging in and out, clearing cookies in between and so on and no errors showing up at all )
--------------- Added [DATE]1432316175[/DATE] at [TIME]1432316175[/TIME] ---------------
Panic over... thanks for your help guys, as it turns out I am just an idiot and had accidentally changed a link while doing something else.... and everything just coincidentally occurred at the same time.... so next time, remind me to look at the blindingly obvious bits FIRST.

xx Sorry, and thanks xxxx