I have had the "reboot problem" since 18th April when I received my Arc. It is not the loose battery problem (reported by others elsewhere) - the phone never reboots due to vibration - most often it is just sat on the desk. It reboots at least 3 to 4 times every 24 hours. I have tried all the suggestions found on lots of forums (Factory Reset, Rebuild Software, etc), but none of these had any effect.
HOWEVER..... 3 days ago I switched off the WiFi. Since then it has not rebooted once. This suggests it is a problem with the WiFi chip. I should add that the reboot would occur wherever I was, with either no router in range or connected to one of 3 different routers. It could be just a coincindence that I haven't had a reboot since I switched off the WiFi, but the 62 hours uptime I now have is three times longer than any previoius uptime since I received the phone. So my current assumption is the problem is the phone WiFi.
So, Sonymax46 - is your WiFi permanently on ? If so, switch it off and see whether it still regularly reboots.
Nevertheless switching off the WiFi is not a permanent solution !! Hence, as soon as Vodafone UK have more Arcs in stock, they have promised to send me a new one, hopefully without the reboot problem.
