I've noticed this when doing Alt-F7 to find usages but it
may apply to all Find Results dialog behavior.
On a Windows 2000 system, if any node of the results tree
expands out to beyond the right edge of the dialog box
then no horizontal scroll bar is displayed and I have to
resize the dialog to see the entire line of text.
On a Windows XP Professional system, the dialog will have
the horizontal scroll bar displayed at the bottom of the
dialog but the scroll bar doesn't work (moving the thumb
doesn't scroll the pane).
This is under Build 109 but I've noticed the same problem
on the previous builds as well.