UDP packet drops when using 2 interfaces

Hi,

I am porting a program to Linux that transfers large amounts
of data via UDP packets. When the program was configured to use
one GigE NIC card on each end I was able to get 200Mbits/sec to
transfer with no packet loss. I then added a second, 100M NIC card
and the transfer rate dropped to below 130Mbits/sec. netstat shows
a large number of UDP receive errors on the 100M interface (no CRC or
packet length errors in the logs).
Using just the 100M NIC I am able to get 90Mbits/sec, so I don't
think there is any problem with the interface. I have tried increasing
the rmem_max/default and wmem_max/default setting with out much luck.

Is there anything else I can try to stop the packet drops?

I am using Redhat 9.0

Thanks,

Ken