Drawing on Textures on the iPhone (larger than 200)

I am currently prototyping an application for a client but have ran into a road block (very early on). One component of the app' is to allow the user to draw on walls but the issue I'm having is that, for some reason, I cannot set (and apply) pixels on textures larger than 200x200 i.e. set pixel works when the image is 200x200 or less but when the dimensions are increased, the ability to set and apply pixels is lost.

(this problem is specific to the iPhone, works in the other players)

Cheers, Josh

False alarm - found that I was calling Apply() twice (once after the other) which must have caused some issues (guessing this is async therefore probably overwriting the initial one?).

Its not directly async but the graphics driver does not handle it blocking, also apply takes till next frame at very least to work.

working on other platforms is caused by the performance of the devices here, it just takes longer than 1 frame to upload textures larger than this.

Thanks Dreamora,

I have noticed that the texture doesn't appear to be updated when trying to render it on the OnGUI call i.e. works if I have the texture attached to a mesh but if I have the texture rendered in OnGUI or try to render it OnGUI (including the mesh on the scene) the texture doesn't appear to be updated. Any ideas?