This has happened to a lot of people, me included.  It manifests with Victoria 4 for sure, although there may be other content that can make it happen.  One thing that you can do that will let you open the files is to locate the .PMD files that are associated with that scene with a file browser and rename or delete them, but be aware that any morphing of figures that you did via morph sliders or with the morphing tool is lost.  As far as I have heard from anyone, there is no other way to work around this problem.  If you do this, you can at least recover the basic figure positioning, posing, lighting, materials and camera settings.  I am pretty certain the morph data cannot be recovered at this time, maybe in a future service release for Poser 7 they'll have a way to recover it.

It seems pretty clear to me that even though this problem manifests with Victoria 4, the fault is with Poser 7, as there is simply no excuse for an application to just blow up and die even if it's reading malformed or corrupt data, that's bad error handling on e frontier's part. 

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