Textfield background color and SDK

I found some very annoying and weird thing. When I compile my app using the 10.5 SDK (on Xcode 3) the
textfields in web pages from WebKit (without style) have a black background color. When compiled using
the 10.6 SDK, they're properly white. This seems absolutely wrong. But I don't have an idea why this is
happening. Does anyone have an idea? I am very sure that this was not happening a while ago with the 10.5 SDK.
I do need it though, as I want to 10.5. I figured out that the text fields have a clearColor set for their
backgroundColor by WebKit. Anyone have an idea why this is happening, and whether there's a workaround?

thanks,
Christiaan