I ran across the same error about a week ago, but can't remember exactly how I got rid of it. I think the problem had to do with Poser not remembering my interface settings, so when a large work area was requested there was no clear space to put it. Try lauching Poser directly by clicking on the "Poser.exe" file in your Poser 4 folder. If you don't see the error message, then it's a good bet that the shortcut that Curious Labs put in your Start Menu Group is faulty. (I'm assuming you are using a PC). To fix just deleat this shortcut, and put a one that you made in there.

If that does not work try going back to the "factory presets" to get your work area back.