Jingpang,
Have you run any Speedtests on your 3G connection speed? I was having similar issues with data connections for streaming: Pandora, Youtube, etc. I ran a ton of Speedtest.net tests (using the app in the market place), and noticed my results were at times as low as .01 and .03 Mbps. A few other tests were in the .10 to .25 (not great) and very rarely .5 to 1.65 Mbps (typical 3G). I called Sprint and they updated some stuff on their end, I performed a hard reset, and things "generally' improved. Some tests are still low but I'm able to do most things. I have a feeling the Photon has some issues handling 3G data. (Probably going to be addressed in the mythical MR).