Dastan,
You have a x440, which has a limited L3 Multcast Table. If you are not running L3 multicast protocols, nor MVR, IGMPv3 or PVLAN, you may want to switch to L2 lookup. That way, you will increase dramatically the scalability (~20x). This is the mac-vlan lookup-key.
If you need MVR, IGMPv3 and/or PVLAN, mixed-mode can be a solution.
Eventually, you can just configure compression for IPMc, if you need just a bit more of entries.
You need 15.3.1+ software for the lookup-key commands.
Please refer to the Multicast EXOS Documentation for the details.