I heard that some custom roms should recieve updates.. I personally doubt... You need to get back to the stock rom to get the next stock OS update... My phone ran via Cm6 since last year November, it never detected any OTA for 2.3 updates until I used passimg method as you just did and got mine finally upgraded.. nice!! its probably due to the modded radio broadbrand of custom roms.. anyway ...migh be wrong...