Hello,
Typically there are two causes for the DMA Channel failures, they are as follows:
1) the BIOS did not init the subsystem.
2) the subsystem is using the channels.
One thing to keep in mind is that Service Center 7.5 was released in 2010 and may not be the best means of determining the failure. I saw in another forum post you were using Service Center 10 as well. Have you attempted to use version 10 on this machine as well? Is it possible to test using the Bootable diagnostics?
Thanks,
Channing