Symptom:
In ISR-G2 running 15.2(4)M4 with integrated switching module, the router did not process any 224.0.0.0/24 on VLAN1, 
which impact anything that utilizes 224.0.0.0/24 including HSRP, OSPF, VRRP. But other Vlan' s  are working fine.

Conditions:
Two ISR G2 router back to back to connected through SM module.

Configure the HSRP in Vlan 1 on both router and make sure that interface status for both SVIs is up/up. Confirm with a ping.
Router#sh standby brief
                     P indicates configured to preempt.
                     |
Interface   Grp  Pri P State   Active          Standby         Virtual IP
Vl1         1    110 P Active  local           20.1.1.2        20.1.1.3

Router#

if sh & no sh on vlan 1 interface then the HSRP Standby details shown as unknown for vlan 1 on both routers. Confirm with 'show standby brief

Router#
Router#sh standby brief
                     P indicates configured to preempt.
                     |
Interface   Grp  Pri P State   Active          Standby         Virtual IP
Vl1         1    100 P Speak   20.1.1.1        unknown         20.1.1.3  >>>>>>>>>>>>>>>

Router#