Hey,
I guess you are using multiple monitors right ?
The problem is that the vanilla client takes the maximum resolution available for
your smaller monitor as the maximum resolution for WoW.
I tried everything, even with the console, it didnt work. (Btw to open the console, try :
/script SetConsoleKey("F7"); then with F7 you will be able to open it, it's written in comment on the thread
viewtopic.php?f=32&t=1100, page 1).
BUT I've found a solution to this.
I used the configuration pannel of my graphic card (ATI) to manually add resolution.
I finally could "fake" that my lower screen could handle the resolution of my main monitor.
It's the solution : if Windows thinks your smaller monitor can use the 1920x1080 resolution, the WoW client will propose the same resolution.
Example for me :
I have 2 monitors, my main is in 1920x1080 and the second in 1650x1050.
So the Vanilla client only proposed the 1650x1050 resolution as max (even in optimized windowed mode, it wasnt a real 1920x1080 so it's not a real solution).
I just added manually (with the ATI control pannel, it's hard to do btw) the 1920x1080 resolution for the smaller monitor. Just ADDED, but not using it because it can't handle it (In Windows I can now choose 1920x1080, but still using the right resolution, 1650x1050).
With this trick the Vanilla client also thinks that my smaller monitor can handle 1920x1080, and I can use this resolution for WoW now.
I'm sorry for my english, it's kinda hard to explain coz it's not my main language, hope you'll still understand what I mean...