There are two parts to the upload.
The upload dialog in 5.5 represents the progress of getting the OVF to the vCloud Director transfer folder. The method of upload is via the Client Integration Plugin (which uses OVF Tool).
If the pop-up window gets to 100% as success, I think the catalog item shows 50% complete and attempts to upload the files to vCenter/ESXi as an import task. If the import task fails, then you need to investigate on the vCenter/ESXi side logs for more details.