Thanks asyx, this is a bug in LWJGL. It happens because STBTTFontInfo.malloc() is the first native LWJGL method you call and the library is not properly initialized (because this particular struct is opaque = has no public fields). It will be fixed in the next nightly build.
In the meantime, a workaround is to call LWJGLUtil.initialize() before STBTTFontInfo.malloc().