I am only able to install 1.9.1 with the following command:
./mage install http://connect20.magentocommerce.com/community Mage_All_Latest --force
The simplest way to ensure you system is fully upgraded is download the 188.8.131.52 update from here:
Then extract all files and using FTP copy this to your Magento directory, overwriting all files. Then manually clear caches by deleting your var/cache folder.