This only happens after I software updated my OS X this morning.
I'm not sure why this happens, but it's happening.. * pulls hair *
It'd be nice if I knew what caused it and how to prevent Photoshop from auto-starting..
Right click on the photoshop icon in the Dock.
Goto "Options" and uncheck "Open at Login".
Open "System Preferences..." from the "Apple" menu.
Select "Accounts".
Select your account if it is not already selected, then select the "Login Items" tab.
Make sure that nothing Photoshop-related is in there. If there is, select it and press the -
button below the list.
FWIW, installing Photoshop CS5 didn't do that to me.