Login Function Works Locally But Not When Live?

[eluser]JamesTaylor[/eluser]
another quick thought if my theory is in anyway correct...

if the server was temporarly rolled back to PHP4 whilst they were checking performance issues that could have caused a serious security issue where login features such mine require PHP5 which is worring? To be fair mine isn't that critical in this occasion, perhaps that just come with the ground on shared hosting?