What error message?
You MAY need to uninstall the trail and run the cleaner before installing the paid versions
-http://forums.adobe.com/thread/1408331?tstart=0
-http://forums.adobe.com/thread/1398961?tstart=0
-and http://helpx.adobe.com/creative-cloud/help/install-apps.html
-using the cleaner after uninstalling and before reinstalling will usually help
-http://helpx.adobe.com/creative-suite/kb/cs5-cleaner-tool-installation-problems.html