Bucket unexpected shut down !!!

Hi,

I have unexpected problem last night with my couchbase server. Two of my bucket suddenly shut down last night. no idea what happening. my apps is on the same server with the couchbase server so network problem should be none. disk space is still have a lot of free space.

there is something strange in the log (look red circle). i see on the "module code" the bucket before is use ns_memcached001, then it became ns_memcached002. what cause that changes this ?

check the log here http://s14.postimage.org/vp9x7qvy9/Log_Image.png (sorry don't know how to add img here :p)

here is the Diagnostic report : http://www.4shared.com/zip/MGrb1BtJ/ns-diag-20120824133751.html