Not sure about your problem. Unfortunately not a lot of liquid users reside in these forums anymore.
Avid did away with their forum for it as well when they end of lifed it. They now have a Media Composer for Liquid users forum. you may want to post there as a lot of current and past liquid users reside there. Check it out if you are still having your problem:
It’s usually in the read me. This from the MC 5 read me: If you are updating from a previous release, you should first uninstall the existing editing
application.
Snow Leopard is fully supported, you should not run into any issues.
As for 3D Objects, you are right. They are not currently supported for CS5 on the MAC OS but should be in the coming months. An exact date has not been set yet.