"The upload path does not appear to be valid"

[eluser]ellipsis[/eluser]
The error I'm getting is the topic's name itself "The upload path does not appear to be valid". The $error that you see in index() is put there only temporarily because seeing that little warning that the variable error wasn't found was getting annoying, but that is not the problem here. When calling do_upload() by clicking the upload button, the page does return with an error so it's being passed fine, but the problem is WHY am I getting "The upload path does not appear to be valid" ? And yes, the directory is writable.