Server Crashing

I get a server bug time to time that crashes my server but no idea what is causing it. I only use 4-5 mods and I can't tell what one is it.

I use
Blocks on Glass
Choptree
Glaygen
Factions
HeroicDeath
Vampire

 

Have you checked your server.log file? That will tell you the cause.

 

And another error that just happened

Hmm never had to before I guess it cant be used when the server is on as I am getting an error saying its in use.

 

What version of craftbukkit are you using? That doesn't look like a plugin issue

 

Using 818

"This server is running Craftbukkit version git-Bukkit-0.0.0-766-g3fc0460-b818jnks (MC: 1.6.6)"

 

Any help on this would be great. I tend to get the second error I posted more often then the first.

 

I am still having this issue has anyone run into it and if so have you found a fix.

Would it help any to say I am now having snow on my map where it has never snowed before....