Hi,
I have this VPS with virtualmin installed and all set, working without any headaches, except this: from time to time (couple days) the webmin service is found stopped… If I want to log in via browser I need to restart it from the VPS. I Also found the proftpd service stopped sometimes (less often).
It looks like you have about 500MB of RAM, and no swap.
Are you by chance using a 64 bit kernel as well?
If so, that would double the RAM requirements of the processes running on your server.
You could always try disabling the services you don’t need… and using a 32 bit distro with any system containing less than 2 or 3GB of RAM would be our recommendation.
However, you may find that you need to increase the amount of RAM available in your server.