I never seemed to have this problem while doing Rails work in Linux, but since changing to OSX everytime I reboot my machine, RVM loses its list of gemsets, but they aren\'t
It appears that your default RVM ruby is not set.
Try running this:
rvm use --default --create 1.9.2@rails3.1
and then rebooting.
If your gemset already exists, you can omit the --create.
--create
rvm use --default 1.9.2@rails3.1