It happens when you're editing expressions, the first time you double-click. When you open the expression window it's all selected by default:
<img src="https://dl.dropbox.com/u/8367729/construct/pics/selectExpression1.png" border="0" />
and you double click on the word 'mangle':
<img src="https://dl.dropbox.com/u/8367729/construct/pics/selectExpression2.png" border="0" />
it selects from the beginning.
This happens all the time for me when editing text objects. I double-click the word to select everything between quotes but it selects the first quotes too.
<img src="https://dl.dropbox.com/u/8367729/construct/pics/selectExpression3.png" border="0" />