I do plan on getting 1GB of RAM and maybe a SSD hard drive too.
I have the Chrysalis Pack installed which shows the available free memory and yes it is always low. But I do believe that I rebooted when it happened and it did not help. I have something to work with now for next time it happens that I can look at available free memory and reboot if needed.
Macmini G4-1.42, 512MB RAM, MorphOS3.9