I'm also having this issue. I'm using Mac OS Lion. I've never downloaded a trial using the Download Manager before. It just seems to be unresponsive to a request to download.
Error 106 indicates that the download is already in your queue. I would recommend completing solution 1 in Troubleshoot Adobe Download Assistant - http://helpx.adobe.com/creative-suite/kb/troubleshoot-download-assista nt.html#main_Solution_1 to reset the download experience.
Alternately you can follow the steps listed in http://forums.adobe.com/thread/981369 to initiate a direct download.
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