ar_kinect nan value in the transform

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I set up ar_kinect and printed the 4x4 pattern on a piece of paper (letter size). Everything seems to be working except that the recognition of pattern is on and off. In particular it only recognizes a transform when the paper is tilted (not perpendicular to the camera) and even then the update rate is slow (compared to what I see on the videos posted). I get the following message whenever a pose is not published

TF_NAN_INPUT: Ignoring transform for child_frame_id "/TEST_PATTERN" from authority "/ar_kinect" because of a nan value in the transform (nan nan nan) (nan nan nan nan)--

here is the roslaunch file for ar_kinect

<launch>
<node name="ar_kinect" pkg="ar_kinect" type="ar_kinect" respawn="false" output="screen">
    <param name="marker_pattern_list" type="string" value="$(find ar_kinect)/data/objects_kinect"/>
    <param name="marker_data_directory" type="string" value="$(find ar_pose)"/>
    <param name="threshold" type="int" value="100"/>
    <remap from="/camera/rgb/points" to="/camera/depth_registered/points"/>
</node>

</launch>

Is this because ar_kinect uses the depth information and there is very little depth info on a piece of paper? If so what is the proper setup?

I will appreciate it if anyone can help with this.