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Unfortunately due to a change in SP1 for Win 7 all 64 bit versions of Fusion older than 6.14.761 will not run. 32 bit versions of Fusion older than 6.14.761 will continue to run as expected. 

Fusion 6.14.761 was released March 15th and is available to all current subscription members. Fusion 6.2.874 also contains the required updates, and was made available to subscription holders as of Jun 28th 2011. Both versions can be found [http://www.eyeonline.com/Web/EyeonWeb/Downloads/DownloadFusion.aspx here.] 

We are working on a patch to older versions and will release it as soon as we are able. The current fix for older versions is to either run 32 bit Fusion, or uninstall Win 7 SP1.