invitation only setting not allowing registered people to login WHY???

Due to all the spamvertisers  ( suprise surprise ) we have decided to change to "by invitation only" but now NO ONE (YES they are registered  ) can login now ...   when you click the login button nothing happens  any ideas why or how to fix that ???? kinda urgent error guys   can someone help me here ????

hmmmmmm... just for fun i disabled by invitation only and the login button does not work all of a sudden .what gives ????  http://oilpals.com 

There's something wrong with your javascript.. Firefox says:

Error: showPopupLoginForm is not defined

Source File: http://oilpals.com/

Line: 1

Try going into administration -> advanced settings ->template

Then uncheck all those cache and compression options. Then clear the cache and try it.

i tried to clear them , in fact i left them unchecked for now .....   try ti now ...... how could there be something  "wrong" with "my" javascript when i didn't change or do anything "different"  it seems when i opted for invitation nly now it does that ...  and btw are our site is not customized in any way other than 3rd party plugins like ultimate articles etc....