I have Lightroom 4 and just bought the Lightroom 6 update. I downloaded 6 and went through the installation and just before the
install is finished, a message pops up and says "A Problem occurred while extracting the archive. Please Try downloading the
Photoshop Lightroom6.0 installer again." I have downloaded it three times now and every this same message occurs? HELP!!!
Try using a different browser to download the file and/or turn off any internet security temporarily in case that is causing a problem.
If you have WinZip or 7Z installed make sure they are up to date. The downloader will probably be trying to use the installed extractor.