In a statement, Argos officials blamed the foul up on "a genuine administrative error" and said only a "small number" of Halo 3 copies were sold.
That may not be good enough for Microsoft officials, who are no doubt apoplectic. The company has spent millions on a high profile Halo 3 marketing campaign that will culminate with elaborate launch events in New York, Los Angeles, Miami and Seattle next week.
Argos may already be feeling retribution from the software maker. A check Wednesday afternoon revealed that the merchant's Web site is no longer able to accept pre-orders for Halo 3. To date, retailers around the world have taken more than one million pre-orders for the game -- an industry record.