Adobe does not support CS4 in 10.11, in fact they don't support it at all, it was dropped from Adobe's lifecycle several years ago.
Apple has changed their OS, and one or more of those changes will have an effect on this legacy software you are trying to use.
This presents you with several choices:
Go back to an instance of your OS when it worked with a version of CS4 that supported it. If you have a Time Machine backup, or the old installer you can do this, or upgrade to a version of Photoshop that is officially supported at this time (CC2015), or done some research and determine if you needed to use CS4 you should not have upgraded to OS 10.11 without an exit strategy, or install a legacy OS on a secondary partition or another drive, however none of these solutions will work until you take OS 10.11 AND Adobe CS4 out of the same equation.
if you feel Apple should suddenly decide they need to fix an issue for a 9 year old piece of software they don't develop and potentially open the door to them fixing all other legacy issues with 3rd party abandonware and possible cause more stability problems elsewhere post here and it's not advised you hold your breath.
apple.com/feedback.