I have CS3 installed already. CS4 refused to install. Where were these mysterious log files? C:Program FilesCommon FilesAdobeInstallers
Well, the log files are sure thorough! In fact nothing could jump out as to why it was failing since the logging was so verbose.
The top of the log file has the address for a log analyzer. That page will install an Adobe Air application which can actually read the logs and link to documents for common failures. Unfortunately, "The module found no solutions to report for the selected log file."