Disk Authorization Problem

I have been experiencing problems with Sims 3 and can no longer play. I have Sims 3 late night and Sims 3 pets installed and have done for years, never experiencing any problems. However, now on the main menu after the opening credits have played a box pops up saying there is difficulty with authorizing the validity of my game and the Sims closes. I have uninstalled and reinstalled both of the expansion packs but the problem keeps reoccurring. 

I appreciate your help and await your response,

Thanks,

Olivia