This has been happening to me as well. I have emailed tech support, and they had be update to the newest client (which seemed to fix it for about 5 minutes), then back to the freezing. I emailed them back stating that I continue to experience the issue and have yet to get a response.
For me, It happens when connecting to my home laptop from XP SP3 / Mac OS 10.6.8 / Windows 7 SP1 clients and connecting from that laptop back out. It doesn't matter whether I'm in a remote location or within the same network, the freezing happens constantly. Sometimes it takes 3 or 4 tries of connecting to see the remote desktop, however it shows the 3 or 4 open connections (even though I never saw the screen).
This has only happened since the version 7 upgrade. Maybe I should downgrade to the newest version 6 build until 7 has worked the issues resolved..