From Wikipedia;
Some motherboards with an LGA 1366 socket support both Core i7 and the Xeon 35xx and 55xx series processors, and advertise support for ECC memory. However ECC functionality is only available if a Xeon is installed, not if a Core i7 is installed.
The Xeon X5650 is not on the Gigabyte GA-EX58-UD4P "CPU Support list".