This is an test case for a problem we've noticed in a custom application that is modeled on the spellchecker.
You can insert additional <text> elements to the main instance (using the "Add text" button below) and spell check them with the spell checker dialog without problems.
However if you delete the entire set of <text>s by deleting their enclosing <textblock>:
And then insert a new <textblock> containing a new <text>:
, invoking spellchecking on the new <text> does not produce the spellchecker dialog. The main form does dim, suggesting the dialog has been invoked, but the dialog is not visible. Inspection in Firebug confirms that the dialog is present, but it appears that it is positioned off-screen (style="...; left:587px; top:253px;...").