I am current on build 2002022203, but I've seen this in earlier builds. Happened with the current XPI (Feb 26, 2002): 1. Go to http://www.mozilla.org/projects/calendar/ 2. Click the link to install the XPI. 3. Watch install progress. Almost everything happens as expected. The install cleanly makes it through all phases until the very end of the "Finishing install... please wait." phase. Then it gives an error, code 999. The install seems to have succeeded, as I can run it. This may be due to earlier installs, however? Repeating the above procedure usually fails, but occasionally succeeds. Once it succeeds, it doesn't seem to fail again, but I haven't tested it that much. I experience this problem usually when I update my browser version, as I need to install the XPI again.
I've asked about this in netscape.public.mozilla.xpinstall, we'll see if we get an answer. I imagine that the windows installer doesn't delete the old installation, so its getting installed twice. Just a guess though.
According to http://developer.netscape.com/docs/manuals/xpinstall/err.html (I don't know if that applies here), but error code 999 is "The files were installed, but one or more components were in use. Restart the computer and Communicator to complete the installation process. On Windows NT, you may only need to restart Communicator as long as you did not replace operating system files." That makes sense in this case, but I don't know how to solve the problem. I imagine if you had quit Mozilla before installing the new version, things would be OK.
OK, that was the problem and I've added in a check for it. That error doesn't show up any longer.
Mass move of libxpical bugs to the Internal Components, per ctalbert.
The bugspam monkeys have been set free and are feeding on Calendar :: Internal Components. Be afraid for your sanity!