E_ADEPT_REQUEST_EXPIRED

I get the message: 

Error getting License. License Server Communication Problem: E_ADEPT_REQUEST_EXPIRED when I try and add books to ADE library (to then transfer to e-reader). I have gone through this forum and looked for help, tried changing time and deauthorising, trashing the .dat file (as suggested in other posts) and reauthorising and nothing makes a difference. Help would be appreciated!