I'm developing an OpenGL engine and I spent some time last year porting parts of it to WebGL. One piece of the engine is a skinnable 2D Gui that is constructed from quads. I render it using a perspective camera with a 90 degree field of view. This has been working quite well for some time, but in the Chrome browser I get something that looks like the window on the left, while in my standalone engine and in Firefox I get something that looks correct (right).

Any ideas as to why this is happening?

NOTE: I do realize that I could be using orthographic projection and I may switch at some point, but what I have really should be working.