We just upgraded from Media Composer 6.0 to a trial version of 6.5.4 at our production company. It is now almost ground to a halt. It's not crashing but we are unable to do anything on it. We are running Mac OS X 10.7.5 2 x 2.26 ghz quad core intel xeon. 22GB 1066 MHz DDR3 ECC memory. ATI Radeon HD 5870 1024 MB Graphics Card. Any ideas whats causing it?