graph empty when new nodes added without their own children

[DON]

I have a basic test graph. This one shows up in the graph just fine.
<Graph>
<Node id="907" nodeTitle="MyLocation" nodeIcon="ngdist50.jpg"/>
<Node id="416" nodeTitle="CentComp" nodeIcon="CentComp.png"/>
<Edge fromID="907" toID="416"/>
</Graph>

but when I add another node/edge to the same parent node 907, the
graph goes blank!

<Graph>
<Node id="907" nodeTitle="MyLocation" nodeIcon="ngdist50.jpg"/>
<Node id="416" nodeTitle="CentComp" nodeIcon="CentComp.png"/>
<Edge fromID="907" toID="416"/>
<Node id="100" nodeTitle="Comp" nodeIcon="Compressor.png"/>
<Edge fromID="907" toID="100"/>
</Graph>

Same when I add another node...
<Graph>
<Node id="907" nodeTitle="MyLocation" nodeIcon="ngdist50.jpg"/>
<Node id="416" nodeTitle="CentComp" nodeIcon="CentComp.png"/>
<Edge fromID="907" toID="416"/>
<Node id="100" nodeTitle="Comp" nodeIcon="Compressor.png"/>
<Edge fromID="907" toID="100"/>
<Node id="170" nodeTitle="Tank" nodeIcon="Tank.png"/>
<Edge fromID="907" toID="170"/>
</Graph>

However, when I add a new node that has its own children, this new
node and all the others show up fine!

<Graph>
<Node id="907" nodeTitle="MyLocation" nodeIcon="ngdist50.jpg"/>
<Node id="416" nodeTitle="CentComp" nodeIcon="CentComp.png"/>
<Edge fromID="907" toID="416"/>
<Node id="100" nodeTitle="Comp" nodeIcon="Compressor.png"/>
<Edge fromID="907" toID="100"/>
<Node id="170" nodeTitle="Tank" nodeIcon="Tank.png"/>
<Edge fromID="907" toID="170"/>
<Node id="819" nodeTitle="RC-C3-GV2-BV2" nodeIcon="RecipComp.png"/>
<Edge fromID="907" toID="819"/>
<Node id="993" nodeTitle="GV0" nodeIcon="BallValve.png"/>
<Edge fromID="819" toID="993"/>
<Node id="922" nodeTitle="GV1" nodeIcon="BallValve.png"/>
<Edge fromID="819" toID="922"/>
<Node id="872" nodeTitle="BV0" nodeIcon="GateValve.png"/>
<Edge fromID="819" toID="872"/>
<Node id="502" nodeTitle="BV1" nodeIcon="GateValve.png"/>
<Edge fromID="819" toID="502"/>
<Node id="673" nodeTitle="CYL0" nodeIcon="Cylinder.png"/>
<Edge fromID="819" toID="673"/>
<Node id="299" nodeTitle="CYL1" nodeIcon="Cylinder.png"/>
<Edge fromID="819" toID="299"/>
<Node id="767" nodeTitle="CYL2" nodeIcon="Cylinder.png"/>
<Edge fromID="819" toID="767"/>
</Graph>

Why are the nodes without children breaking the graph?

Thanks,
Don