Under Windows 7, there will be issues if your Runtime is within Program Files (which the Poser 7 installer considers to be the "proper" place). Windows will try to stop applications writing to sub-folders under Program Files.

I'd advise either moving your Runtime to your documents, or the entire Poser installation; you may have fewer hassles with the latter.

I don't know why it used to work and now doesn't, but something changing within Windows could bring this about.