purple ssh status for some clients

Hi, we have a huge setup of xymon(nearly 300 clients and a server).Some of the clients ssh status is purple.it is not updating. History log says :2009-11-05 12:40:29 Will not update /opt/xymon/data/hist/a.b.c.d.ssh - color unchanged (purple)-hosts .bbhosts entry is also ok in hosts file,Wt could be wrong?how to troubleshoot it?

-- Pankaj V. Dorlikar