some slave nodes failed when crawling

[luozhiguo]

Hi, guys:
        I established a search engine with 16 nodes using nutch0.8.1, and
tried to crawl some urls.  When crawling urls, I found some slave nodes
failed. These failure slave nodes didn't died, but all process concerned
nutch were stoped.  I telneted to these nodes and found no nutch process
were running（ps -aux | grep nutch).  Does anybody know what's wrong and how
to add slave nodes into the running system? Thanks a lot.

Cheers,
Roger