BLANK Cloud Screen http://forums.adobe.com/message/5484303 may help
-and step by step http://forums.adobe.com/thread/1440508?tstart=0
-and http://helpx.adobe.com/creative-cloud/kb/blank-white-screen-ccp.html
or
Sign out of your account... Uninstall... run the Cleaner...
-Restart your computer... Sign in to your account... Reinstall
-using the cleaner after uninstalling and before reinstalling is needed
-http://helpx.adobe.com/creative-cloud/help/install-apps.html (and uninstall)
-http://helpx.adobe.com/creative-suite/kb/cs5-cleaner-tool-installation-problems.html