ok thanks for that Ray and certainly interesting.
I have tried setting the validation up this way
$WAFV_Errors .= WAValidateRX(((isset($_FILES["EventImage"]))? preg_replace('/.[^.]*$/', '', $_FILES["EventImage"]["name"]) :"") . "","^[a-zA-Z0-9_.-]+$",true,2);
to only allow alphanumeric, underscore, hyphen and period and still getting the internal server error http://prntscr.com/onmb1e - if I rename the file to have spaces but no apostrophe then the validation works fine