After some weeks I tried to start my RPI again to setup a local NAS.
I knew there was Arch on the SD card so I just tried to start it. I connected it to a HDMI screen and it seemed to boot correctly. Then suddenly it crashed and seemed to reboot but I got nothing on the screen again.
I thought it might be a corrupt system so I reinstalled Arch (latest version for ARM) on the SD card and tried it again - same result.
I don't know why this happens. I can actually log into the system but about 30 secs after start it crashes.
When it starts all 5 LEDs are lit up but if it crashes only PWR and ACT remain lit up. FDX, LNK and 100 are off after the crash.
After that I disconnected everything except for the power cable and the ethernet cable so that I could control it via SSH - same crash as before.
I use a power supply from the RS store with 1200mA at 5V without any external devices attached to it. Only ethernet/power cable.
I don't think that it broke in any way. All the time it was stored in its pink plastic case.
Do you know any advice what could have happened?