Nobody can tell you anything without proper system info or other technical details. Start by reinstalling the program.
As Mylenium says, we don't even know what OS you're using.
What eye dropper are you using?
In your preferences, what is the setting for using system color picker? Is it on or off? Does it behave differently if you change that?
Apologies Ive never posted in forums before and not sure on what information to give out.
Im currently running OS X Yosemite
macbook pro 15" late 2011
The eye dropper tool is the built in tool example the eye dropper tool in the character menu when selecting a colour for text.
as for settings of colour picker, I can't seem to find what your talking about. Heres what happens immediately after I select the colour dropper tool.
That's one of several bugs that happen when you try to use such an old version of AE on a new Mac OS. CS 5.5 is not supported on Yosemite.
In the preferences, there should be an option to use the system color picker (or something like that). That usually fixes this issue. The only other fix that I know of is downgrading your OS or upgrading your AE.