mcelog error message

Server:IBM x3850-X5
Environment: RHEL 6.2 X86_64

/var/log/mcelog:
Hardware event. This is not a software error.
MCE 0
CPU 16 BANK 0
MISC 2
TIME 1410692744 Sun Sep 14 19:05:44 2014
MCG status:
MCi status:
Error overflow
Corrected error
Error enabled
MCi_MISC register valid
MCA: BUS Level-3 Generic Generic Other-transaction Request-did-not-timeout Error
16:2> BQ_DCU_READ_TYPE BQ_ERR_HARD_TYPE BQ_ERR_HARD_TYPE
timeout BINIT (ROB timeout). No micro-instruction retired for some time
39:3> bus transaction received hard error response
failure that caused IERR
two failing bus transactions with address parity error (AERR)
STATUS d8001dc000020e0f MCGSTATUS 0
MCGCAP 1000c18 APICID 80 SOCKETID 2
CPUID Vendor Intel Family 6 Model 47

why?