Jeff,
Try to create a new LBK, and import layouts one by one from the corrupt file into the new one. You might be able to import some/most of the layouts, altough some layouts will probably give the same error message.
It is a good idea to first open a similar LBK (with same masters, titles, etc.), and then open a new file with those settings loaded.
Gergely Kmethy
VP, Customer Success, Graphisoft