This isn't related. I see these all the time and I think it's due to how TRS19 and up parse a route and session. In the olden days, a whole route and whole session were loaded into memory. This caused really bad performance due to everything being loaded at once as the program ran out of resources. Starting with a late service pack in T: ANE, routes and sessions are now carved up into smaller chunks so that they load up quicker and run better. Since the asset isn't in the scene, then this message appears. If it was an error, there would be a red X.
The freeze is something else. This usually occurs if the graphics are too heavy for the CPU and the rest of the system to handle. You may want to lower your settings and try again. If you are using regular hard drives and not an SSD, defragment your hard drives. This helps a lot.