Why is UIGroupTableViewBackgroundColor causing Xcode 4.2 to choke?

I'm using Xcode 4.2 on Mac OS X Lion 10.7.3 and for some reason, every time I set UIGroupTableViewBackgroundColor as the background color on my UIView, the compiler refuses to build my app.

When I open the "newly corrupted" XIB as XML and remove the offending XML represenation of the background color, the app compiles. I am able to apply the background color in code, but doing so in Interface Builder fails miserably.

Here's the code that chokes Xcode. Any clue why this is happening?

<object class="NSColor" key="IBUIBackgroundColor">

                <int key="NSColorSpace">10</int>

                <object class="NSImage" key="NSImage">

                    <int key="NSImageFlags">549453824</int>

                    <string key="NSSize">{512, 1}</string>

                    <array class="NSMutableArray" key="NSReps">

                        <array>

                            <integer value="0"/>

                            <object class="NSBitmapImageRep">

                                <object class="NSData" key="NSTIFFRepresentation">

                                    <bytes key="NS.bytes">TU0AKgAACAjFzNT/xczU/8XM1P/FzNT/xczS/8vS2P/L0tj/xczU/8XM1P/FzNT/xczU/8XM0v/L0tj



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xczS/8vS2P/L0tj/xczU/wANAQAAAwAAAAECAAAAAQEAAwAAAAEAAQAAAQIAAwAAAAQAAAiqAQMAAwAA

AAEAAQAAAQYAAwAAAAEAAgAAAREABAAAAAEAAAAIARIAAwAAAAEAAQAAARUAAwAAAAEABAAAARYAAwAA

AAEAAQAAARcABAAAAAEAAAgAARwAAwAAAAEAAQAAAVIAAwAAAAEAAQAAAVMAAwAAAAQAAAiyAAAAAAAI

AAgACAAIAAEAAQABAAE</bytes>

                                    </object>

                                </object>

                            </array>

                        </array>

                        <object class="NSColor" key="NSColor">

                            <int key="NSColorSpace">3</int>

                            <bytes key="NSWhite">MCAwAA</bytes>

                        </object>

                    </object>

                    <string key="IBUIColorCocoaTouchKeyPath">groupTableViewBackgroundColor</string>

                </object>

Here's what it looks like in Xcode:

Any clue what could be causing the problem?