When we went to LAX in PE in late 2011, we were only VA Red but were able to select any seats in the PE cabin apart from Row 10. When hubby booked a return trip to LAX in PE about 9 months later (booking about 6 months out), he was Silver but he was restricted to selecting from Row 14, every other row was showing as blocked! He did ring the Guest Contact Centre after he'd booked and they allowed him to select Row 11 at that time but apparently they didn't put it in the system, as when he checked his booking about 8 weeks out, he was still in Row 14 both ways! However, he hit Gold before the trip and the online seat selection map (this was just prior to Sabre) then "opened up" and he was then able to select any row. (These were all paid fares, not reward seats).
It appears from the above posts that now Rows 10 and 11 are reserved for Gold/Plat but not Silver as the OP was unable to select seats?