So what I did to get this working is edit hidden.tpl and replace it with this:
<input type="hidden" id="current_url" name="current_url" value="<?php echo 'http:/domainname.com',$_SERVER['REQUEST_URI'];?>" <?php echo $attr ?> />
Then I changed the Field Name & Display Name in the Forms Manager to "current_url" for the Hidden Field Type
You can replace your domain name in place of "domainname.com"
I dont know how this effects anything else with a hidden field, but I only have that one so this works for me.