I think you should contact CL's tech support. Since the Poser installers are the only applications that you're having problems with, they're the most likely to have seen this before and have a fix. I assume you're trying to run the install from the Original Poser CD and that you've tried redownloading the updater. I seem to recall that CL has their own install rather than the standard Windows installer or one of the third party packages - no telling what it's trying to do.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken