corrupt file - won't save as

My storyboard pro file seems to be corrupt. I can open it (265meg) but as soon as I do a save as - or an archive, I suddenly start to lose layers and drawings and the new saved file is only 42 meg. Apparently, the draw files are there until I try to modify the document. I’ve even tried to copy the file to another hard drive, but when I do it says there’s data that cannot be read then quits out the duplicate. So I’m totally stuck with my file that won’t save as, won’t duplicate, won’t archive - but oddly, it will save (regular save) But that is way too risky to work that way. Please advise.OSX LionMac tower 2 x 3 GHz Dual-Core Intel Xeon 16g ram

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