instance in scalr farm rebooting continuously

Answer:
Most likely, SNMP monitoring does not work or event handler configured
improperly.

Steps:
# apt-get install snmpd snmp
# vim /etc/default/snmpd
----------------------
#SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid 127.0.0.1'
## remove the localhost parameter from the end of the line
SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid '
----------------------
# vim /etc/snmp/snmpd.conf
----------------------
com2sec readonly default cc54b971b0bd1a
group MyROGroup v1 readonly
group MyROGroup v2c readonly
group MyROGroup usm readonly
view all included .1 80
view system included .iso.org.dod.internet.mgmt.mib-2.system
# context sec.model sec.level match read write notif
access MyROSystem "" any noauth exact system none none
access MyROGroup "" any noauth exact all none none
access MyRWGroup "" any noauth exact all all none
#
syslocation Amazon EC2
syscontact Nativetung Inc.
----------------------
# vim /etc/snmp/snmptrapd.conf
----------------------
authCommunity log,execute,net cc54b971b0bd1a
----------------------
# /etc/init.d/snmpd restart

Still have the same issue... ?
Have you configure the event handler?

Login to scalr --> Settings --> Core settings --> add the event handler url and IP address as same as the scalr machine

Now pull up ur sleeves and lets explore more now..