Thank you for the information, Jack. We will need more time to research on this issue. We will get back to you with more details.
Also, please let me know the manufacturer and the model or part number from the main board integrated on the system.
My motherboard is an ASUS P6X58-E WS.
Note that this CPU and motherboard combination worked well with linux-3.1 without any warning.
Only a software upgrade to linux-3.2 caused this error message.
Further checking on the changelog for the debian package intel-microcode shows that rev-0x13 microde for cpu 0x206c2 was released on Sept. 2010 and withdrawn 2 months later on Nov. 2010.
It's unclear why the newer linux image would be requesting a microcode version that was withdrawn a year earlier while the previous linux version, released in Jan 2011, did not.