Server Crashes after 30 mins with strange error.

Hello so im getting this really persistent crash that requires me to manually restart as rtk cant detect it...
it happens randomly at any time on the server and cant seem to replicate it. the error explain nothing about what caused the crash (at least from what i can see, as i dont know really)
heres the crash log: http://pastebin.com/9aiur2Ev

if anyone can figure out what plugin is causing this or what sort of thing triggers this crash id be greatly thankful!

We are running 1.5.2 as we are a creative server that requires use of plugins not yet updated to 1.6+

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