1.6.3 works just fine in CraftBukkit 1.1-R1. 1. Make sure you're using the latest version. Also, if/when something like that happens, the server log from when the error happens is pretty much essential to figuring out the cause. 2. I'm not sure what you're seeing, but if you do have that set to 0, it's not Factions causing it; if noPVPDamageToOthersForXSecondsAfterLogin is set to 0, the routine which checks for that immunity is completely skipped. 3. Much like above, without an error log from the time that happens, I can't help you. There is no clear reason why that might happen based on auditing the related source. Hmm... like above, if something like that happens, a copy of the error log from when it happens would still be very useful.