Paste and Paste Special Functions Are Disabled. How to enable those again

Hello Everyone,
Can anyone tell me how to enable the paste functions in excel 2007 version. When i am working suddenly the paste and paste special functions are disabled i don't know why. I tried all the things i knew but the problem was not solved.Earlier i wrote a macro to remove hyperlinks. I deleted that macro but the problem still persists. Can any one tell me how to enable it again? I am attaching the screenshots. please check it and tell me the solution.