Remember that it's *366* days in advance...so if you want a reservation starting on June 5, 2008, you need to book it on June 4, 2007. I've gotten hit by that before, especially when the year I'm booking is a leap year, as 2008 is. Also, once the reservation is booked you can modify your starting/ending days, so if you're flexible, you might want to try to start booking your trip for a day or two before you think you might be arriving, and you can always call them and change your arrival date later. I think that you can only book a maximum of 7 nights at a time, though.
The phone-in reservation office opens at 8:00 PST, and that seems to be when the on-line reservations go live, also. I'd suggest calling AND trying the internet at the same time.
The Lodge is a wonderful location - we stayed there just after Christmas this past year and they have upgraded the rooms since I last stayed there. The rooms are still old and a bit rustic - it's more like a Holiday Inn than a Westin or Marriott - but you sure can't beat that location just across the road from Yosemite Falls!!!