Sometimes one of these works for a similar problem in Windows Explorer:

Tools|Options|General|Ignore other applications (uncheck it)

--- or ---

Close Excel and
Windows Start Button|Run
excel /unregserver
then
Windows Start Button|Run
excel /regserver

The /unregserver & /regserver stuff resets the windows registry to excel's
factory defaults.

Maybe one of them will work for you.

Shirley A. Smith wrote:

When receive excel attachments in Microsoft Outlook, when try to open
attachment, it opens the excel application, but to a grady shade background,
the attachment never opens. When close the excel application, a box is
displayed saying the system cannot find the file specified.

--

Dave Peterson