The file dialog has often given problems. It works like a charm in certain cases, whereas doesn't work in other cases. When you hit the File Download, there are two dialogs that typically show up:

1) File Download dialog prompting the user to select whether to download, save or cancel
2) File Download dialog with information about the dialog itself.

It looks like there is a race condition here and depending on which dialog wins the race, test fails or passes.

I am using GEM9.1.404 and this problem only occurs when I use the object repository to describe the elements.
For example,
This code works fine:

Repository("SC0031_ViewNote").check_exists()
ie = Browser("title:=/^View Note:.*/")
ie.Link("href:=/.FileDownload./").click_without_blocking
dia = ie.Dialog("title:=/.*/")
but = dia.Button("index:=3")
but.click()

But this doesn't!!!!!

Repository("SC0031_File_Link").click_without_blocking
Repository("SC0031_FileDownload_Cancel_Button").click

Where the objects are described using XML as:

<Object Name="SC0031_ViewNote" Type="Browser">
<Def Type="ParentObject">
<Description>
<title>/^View Note:.*/</title>
</Description>
</Def>
<Object Name="SC0031_File_Link" Type="Link">
<Def Type="ChildObject">
<Description>
<href>/.FileDownload./</href>
</Description>
</Def>
</Object>
<Object Name="SC0031_FileDownload_Dialog" Type="Dialog">
<Def Type="ChildObject">
<Description>
<title>/.*/</title>
</Description>
</Def>
<Object Name="SC0031_FileDownload_Save_Button" Type="Button">
<Def Type="ChildObject">
<Description>
<text>&Save</text>
</Description>
</Def>
</Object>
<Object Name="SC0031_FileDownload_Cancel_Button" Type="Button">
<Def Type="ChildObject">
<Description>
<index>3</index>
</Description>
</Def>
</Object>
</Object>

Shruthi has investigated this issue and finds that WatirNativeObject layer of WET needs some changes. It is high risk to do this before 1.0 final.