VLAN trunk between Cat 6500 and Force 10 S50

Hi all, I am trying to establish a vlan trunk between a 6500, which runs native IOS, and a Force 10 S50 which runs SFTOS 2.5.1. Since I want it transparent to end users behind the S50, I configure the S50 to do the tagging. Basically, ports 2-30 of the S50 are configured as VLAN 100, ports 31-48 are configured as VLAN 101. Port 1, which is connected to the 6500 is within both VLAN 100 and 101. All ports are tagged. On the 6500 side, the port is configured as a switchport in trunk mode, which encapsulates 802.1q and allows VLAN 100 and 101. I felt this was a simple problem but it took me two days without being able to figure out why my configuration could not work. I ping'ed from a computer behind the S50 to a port of 6500, which is within the same subnet and I saw the arp reply from the port of 6500 using port monitoring. However, the arp reply messege obviousely did not go back to the computer. If someone has a clue, I would be really appreciate if some light can be shed. Shu