I have had same trouble before and again this evening with great frustration. Removed and reloaded desktop application; removed files in Local/Adobe/OOBE etc. It may however not be the Adobe programs at fault, but rather your internet connection and possibly proxy settings.
In the end I found the answer here: see section 4 of this page
http://helpx.adobe.com/creative-cloud/kb/unable-login-creative-cloud-248.html
In my case I had tried all the remedial suggestions (several times) without any success [ and previously with Adobe customer support at great length] and in the end it came down to my internet settings on the brower and not the programs.
Changing the setting to "automatically detect settings" fixed it straight away. That could have saved a lot of time and frustration.
Chris Wiltshire