Internet Multicasting Puzzle

All:
I am trying to figure out why a client can't see UDP packets generated from
my Multicasting server. Here are the facts:

Server-
- Mandrake Linux v9.1 OS
- Perl UDP Socket
- DSL/ppp0 interface to Internet
- Destination, 234.x.x.x:PortB
- TTL = 255

Client (across Internet)-
- Java app./socket
- Linksys DSL router (DMZ - no security settings for testing purposes)
- DSL connection to Internet
- Multicast Group added through Java app.

Verify-
- Ethereal sniffer on both server and client
- Packet Length = 104 bytes
- TTL verified
- frame captured - sent 88 bytes from 207.x.x.x:PortA to 234.x.x.x:PortB

The client can't see the messages!

Any suggestions of what to try would be greatly appreciated.
Thank you in advance,

Moose