my return key on Macbook pro doesn't work

Hello there,

It sounds like the return key is not working on your computers built in keyboard. I would use these steps from the following article to help isolate and resolve the issue:

Try logging into a different user account. If the issue does not occur when logged into a different user account, then troubleshoot for software issues.

You may have accidentally set an option that changes how your keyboard operates.

Choose Apple menu > System Preferences, click Dictation & Speech, and then click “Text to Speech.” If “Speak selected text when the key is pressed” is selected, deselect it or press Set Key to select another key.

Choose Apple menu > System Preferences, click Accessibility, and then click Keyboard. Make sure Slow Keys is turned off. If Slow Keys is on, you must hold down a key longer than usual before it’s recognized.

Choose Apple menu > System Preferences, click Language & Text, and then click Input Sources. Select the checkbox next to Keyboard & Character Viewer, and then select “Show Input menu in menu bar.” Open the Input menu and make sure the correct keyboard layout is selected. To see the keyboard layout, choose Show Keyboard Viewer from the Input menu.

From: OS X Mountain Lion: If keys on your keyboard don’t work

http://support.apple.com/kb/PH10680

Thank you for using Apple Support Communities.

All the best,

Sterling

Try another keyboard. If it works ok, the internal one is probably damaged and needs repair.