Computer says cd blank but it has data

i have a data cd that i have used repeatedly for months with no problem. a few days ago when i put the cd in, autoplay pops up and says what do you want to do with this "blank" cd. i click on my computer, access the e drive and it shows the cd is there and say 230 of 702mb free but when i double click on it nothing open like its a blank cd.... whats goin on?? please help!