Thank you all for your assistance.

Connie had right answer.
In the grub boot loader all of the available Kernels are there and can be 
booted.  Top of the list was 6.4 .
When we had a major power outage the system, shut down by the UPS, and  was 
manually rebooted and the orrig. 6.4 Kernel was loaded and no Ethernet - 
transmit.   According to "ifconfig" the Rd had a large number and the Tx had 
0.
On this system its hard to see as the boot happens very quickly and if you are 
not looking for it you miss it.
In the "grub" boot loader all 6.4 , 6.4 elrepo, and 6.5 kernels were there.
If you don't select "elrepo", it boots with 6.4.
Rebooted using the "elrepo" kernel, solved the problem.

Ethernet is now working.

Next Question:
How do I modify the boot loader to put the "elrepo" kernel first in the list?

The hardware works perfectly with SL 5.4 to SL 5.10.
It will work with a 32 bit SL 6 but not with the 64 bit SL 6.1 -> SL 6.5.
I would assume some where in the code a variable definition's length did not 
get changed to 64 bit.  Or some how a 32 bit module or driver was linked in.
The odd part is that SL 5.4 as a 32 bit system worked, SL 5.5 -> SL 5.10 as a 
64 bit worked.
Hope upstream builder fixes the problem.

Thank You All for the expert help.

Larry Linder