This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.
When importing a LOD manually in the Static Mesh Editor the editor will freeze indefinitely.
1. Open UE4
2. Import a FBX or use an existing Static mesh with no LODs
3. Open the Static Mesh
4. In the details panel go to LOD Import
5. Select the drop down and select 'Import LOD Level 1'
6. Select an FBX to import as LOD Level 1
Results: The editor will indefinitely freeze
Expected: LOD 1 will be imported without a substantial freeze.
Head over to the existing Questions & Answers thread and let us know what's up.