10.3.9 Freezes On Restart



I have an absolutely lovey 800 MHz G4 iMac, 256MB RAM, with OS X 10.3.9 installed.

Sadly, my iMac freezes often on restart, without any apparent reason.

When starting up, I sometimes login successfully, but mostly the computer freezes after entering the login password (rainbow spinning wheel), or after loading desktop and dock (but the menu bar never appears). Zapping PRAM sometttimes helps, but most times I have to restart about three or four times, each time it seems I progress further and further. At times the computer finally starts up correctly, but when I first launch an application (iTunes, iPhoto, AppleWorks or Safari, rarely anything else), then the freeze occurs and it takes another few restarts for everything to work properly.

Sometimes I even get some (unix?) text-based screens and listings coming through the desktop pattern during the freezes.

It seemed to me that the problems appear often after putting the computer to sleep overnight, so I decided to always switch it off fully, but that is even worse. I now learned to leave the computer running for a day or two in the row, without putting it to sleep, I may work without a slightest problem, but when I finally shut it down and later start up, again I have to go through several freezes and restarts. I do not have any energy settings or screensavers activated.

I tried to back up my files and I erased the disk and installed completely anew my OS X 10.3.9, but to no avail. The problem persists.

I have tried also "repairing permissions" (not that I am clear what exactly this does), but have not tried it yet after starting from another system CD.

I do not run any difficult software, the only 3rd party hardware I have attached is USB iMic, Cannon inkjet printer and BT Broadband modem (via Ethernet port).

Is there any advice you might have for me, please?

Many thanks!