NiftyGui Tabs Not Visible

<?xml version="1.0" encoding="UTF-8"?>
<nifty xmlns="http://nifty-gui.sourceforge.net/nifty-1.3.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://nifty-gui.sourceforge.net/nifty-1.3.xsd http://nifty-gui.sourceforge.net/nifty-1.3.xsd">
    <useStyles filename="nifty-default-styles.xml" />
    <useControls filename="nifty-default-controls.xml" />

    <screen id="mainScreen" controller="com.blockhouse.BuildAChair.NiftyOptionsManager">
        <layer id="specPanelLayer" width="100%" height="700px" valign="bottom" childLayout="vertical">
            <panel name="panel" height="*"/>
            <panel id="specPanel" name="panel" align="right" valign="bottom" height="700px" width="600px" style="nifty-panel-no-shadow" childLayout="vertical" visibleToMouse="true" padding="5px" >
                <effect>
                    <onShow name="move" mode="in" direction="right" length="250" startDelay="0" inherit="true"/>
                    <onHide name="move" mode="out" direction="right" length="225" startDelay="0" inherit="true"/>
                </effect>
                <control id="specTabs" name="nifty-tabs" buttonWidth="50%" buttonHeight="50px" >
                    <control id="fabTab" name="nifty-tab" caption="Fabrics">
                        <panel id="fabSec" childLayout="vertical" backgroundColor="#8001" padding="4px" paddingLeft="4px" paddingRight="4px" paddingTop="4px" paddingBottom="4px" width="100%" height="100%" >

                        </panel>
                    </control>
                    <control id="stnTab" name="nifty-tab" caption="Stains">
                        <panel id="stnSec" childLayout="vertical" backgroundColor="#8001" padding="4px" paddingLeft="4px" paddingRight="4px" paddingTop="4px" paddingBottom="4px" width="100%" height="100%" >

                        </panel>
                    </control>
                </control>
            </panel>
        </layer>
    </screen>
</nifty>