I’ve have blank templates after exporting and importing using the native WordPress importer.
So far I’ve tried going through plugins one by one and clear the BB and Server Caches.
When I deactivate all plugins except for BB, then the template will show up momentarily. If I change to a different template it will then become blank again.
We recently discovered a small bug with BB in the WP importer/exporter. We have a patch released and you can download the new importer/exporter from this thread. Make sure to remove the old one beforehand, but that should get you fixed right up!