Happen to me enough times for me to stop playing..After I played WH for 3+ years etc..I was dying for SH to be released now I just don't care...yet, I seem to check the forums to see what's happening.
I have only been kicked to the XMB once out of all the glitches I have experienced. The XMB kick occurred on the same night I downloaded the latest PlayStation 3 firmware. I think it's 4.25? It happened the same day the firmware was released and after playing two games of Starhawk directly afterward it happened on my third game playing a CTF match.
I was flying in a Hawk, and right as I launched a Homing Missile to get a kill I got a black screen and I didn't know what was going on. My tv's input listing came on, and then the XMB loaded.
Aside from the XMB, tanks have also been causing freezing as you're attacking or when you get a kill.
Id' say it happened a good 10-15 times in the first couple of months, maybe more, but I honestly can't remember. I haven't played for over 2 months now though.
Played tonight for the first time in a while, by the 3rd map, the server was migrated to me, I was in a hawk, trying to flakk someone, and bam, kicked to XMB.
It really seems like its a hawk thing.