:(Have just purchased GSX level2 expansion and I cannot get it to load. It gets as far as "baggage tractor\sound ai\sound ai.cfg" and freezes!
Must be something related to the antivirus so, be sure you configure it to exclude the whole Addon Manager folder from scanning, and disable it while installing.
If it's not the antivirus, check if you have enough space on the Windows drive (usually C:). Even if you install into another drive, the installer will still require some space in the Windows temporary folder during the installation so, if you are low on space on that drive, it might get stuck.