after reboot of my rac nodes, i found that one of the nodes is having problem in starting up CRS i.e.
CRS-0184: Cannot communicate with the CRS daemon
$ less /u01/app/crs/log/nodename/crsd/crsd.log
2009-09-09 09:52:49.154: [ COMMCRS]clsc_connect: (10076b610) no listener at (ADDRESS=(PROTOCOL=ipc)(KEY=OCSSD_LL_nodename_))
2009-09-09 09:52:49.154: [ CSSCLNT]clsssInitNative: failed to connect to (ADDRESS=(PROTOCOL=ipc)(KEY=OCSSD_LL_nodename_)), rc 9
2009-09-09 09:52:49.156: [ CRSRTI] CSS is not ready. Received status 3 from CSS. Waiting for good status ..
sometimes when CRS server reboot it try to create sockets under /tmp/.oracle or /var/tmp/.oracle and there are already previous socket files...which are protecting to create new sockets.
using root user remove all files under /tmp/.oracle or /var/tmp/.oracle
restart CRS on faulty node or even reboot that machine!