Hello vstrinski,
Sorry about the time lag in getting back to you. You were right about the processor chip not being the problem. My machine was built just last summer, 2012-7-12, yet it came supplied with a relatively old motherboard P/N 6FW8P (A02). SATA port 1 died, so Dell warranty service was out and replaced the motherboard with an ancient refurbished (aka "used") P/N M1GJ6 (A00); I had expected the replacement to be P/N D881F (A05), so this was disappointing. After the motherboard swap, the Memory Failure error message persisted, so after trying anything and everything I could think of, I decided to pull the motherboard and inspect the CPU socket with a magnifying visor, since the replacement motherboard was a used part. Low and behold, there where three groups of bent or slightly displaced pins in the LGA1377 socket. Using a hypodermic needle and an X-Acto knife, I gently moved the pins back to their correct positions, replaced the CPU, and for the first time, the machine booted with no memory failure on DIMM2 BIOS message.
What level motherboard is installed on your T7500? The easiest way to find out is to download the Passmark Performance Benchmark R8 program and run the program called PerformanceTest in trial mode. There is a Dell service program that also displays the motherboard's part number and service level, but I can't remember which one.
See: www.passmark.com/.../pt_download.htm
This is a very useful tool and measuring and managing the T7500. Run the PerformanceTest, then look under the heading System and read down the column This Computer for Motherboard Model and Motherboard Version.
I just installed the 2nd CPU riser kit with a second Xeon X5560 processor, now the machine won't complete POST - I am getting an amber power button and blinking 2-3-4 lights which the Service Manual describes as Pb7. The debugging never ends it would seem.