Vixen 3 shows it is not responding

When I load a sequence in Vixen 3 it is very slow and shows the program as not responding but eventually loads. I am getting very choppy audio on playback and the program seems to consume a very large percentage of the processor capability and memory. I am running Windows 7 64-bit with an Intel e6850 dual core processor at 3.0 ghz and 4 gb of ram. I am using the latest release (3.0.7 I think) downloaded and installed today. I had the same problem with earlier versions. The sequence I am running is imported from Vixen 2.1 and only has 72 channels. Any ideas on what may be causing the pc to bog down with this program?

Thanks,
Ken