When I try to use the Add to Mastercook bookmarklet, it says I must enable cookies. I have done this, restarted the computer, but it still says I have to enable cookies.
Have you double checked your cookies settings? Go into Google's settings. When the Settings tab opens search for cookies in the upper right corner. Click on the Content Settings button that appears. In the area where you selected Allow Local Data to be Set click on the All Cookies and Site Data button.
Also, in the Google Chrome window to the right of where you type in a web page address there is a star icon. Do you have another icon to the left of it that looks like a cookie with a X through it? If so, click on it and allow MasterCook to set cookies.
Furthermore, you could try Manage Exceptions and type MasterCook in there to see if that solves it: https://support.google.com/chrome/answer/3123708