After much experimentation and deliberation, the problem turned out to be that the .java stuff on my computer wasn't in the new Windows Registry. When I attempted to load Panoweaver, an error message (PW's? Windows'?) directed me to a borland.com site, which in turn sent me to java.com to download the latest Java software, which I did.
That is not the version PW apparently wants to see. I reinstalled PW from the distribution files still on my computer, including the Java installation (slightly earlier version) with it. This did not fix the problem as the two versions apparently conflicted.
I ended up removing both Javas AND PW completely (keeping my c&f folder - whew!) and reinstalling with a newly downloaded Trial Version and re-entering the license key info. This cleared up the problem.
Thanks for your input!