We have two QC11 environments. One for production and one for test.
I just exported (from our production installation) our largest project and created a .qcp file that was just under 2GB. That went without error.
I switched to our test environment and imported the same .qcp project file. It went (apparently) smoothly with no error messages.
I can now see the project in the list of projects. But it is unavailable and appears deactivated. I have attempted to Activate it by right-clicking and choosing Activate but all of the right-click menu options are grayed-out, including the option to delete the project.
There is one menu item available. Ping Project. And it returns "Ping finished successfully."