I'm running 10.4.11 and this machine is a year old. I have two user accounts on the same machine and toggle back and forth between them with no problem.

Two weeks ago I had a major "grey curtain of death" crash. I restarted the machine successfully and it hasn't happened again. However, there seems to be a lingering problem that only started after the crash: my display sometimes suddenly changes colour. One moment the colours will be true, the next, everything looks too blue. The whites go sort of light lavendar, the blues go grey-blue, etc. It's like an overlay the colour of a robin's egg has been placed on the screen. It seems to happen most when I toggle back and forth between user accounts. When I restart, everything goes back to normal.