Check if your Java (should be Apple MRJ 2.2.5--check your Utilities folder) is up to date for starters, and upgrading to OS 9.1 or better (as much as you can) will help.

Your LW error message should have had a "copy" button on the error dialog box, or alllow you to click in the message and select all/copy.

Successful downloads can be found in the folder "Shared", so search for it on your HD. Then just drop the files on QuickTime player or whatever program you use to play your files. Rebuilding the desktop can't hurt, and might help the Launch button set the defaults.

A newer version of LW is in the testing stages now, so all this could change pretty quickly.