Upload Data From Excel

I am having problems uploading Excel 2007 data to our web site that contains
payroll data. We have no problems on Windows XP Service pack 2 machines
running Excel 2003, but when we try the same operation on a Windows Vista
computer running Excel 2007 we receive 3 error messages:

Error: Unable to initialze WorkBook member

Failed to start Excel

Access denied. Contact your administrator

In Internet Explorer, I have added the web site to the managed web sites as
always allow and turned off the pop up blocker. Automatic prompting for file
downloads has also been enabled. Active scripting and scripting of Java
applets has also been enabled. Also, I have Check for newer versions of
stored pages enabled. The newest version of Java has been installled on the
computer as well.

In Excel, under Active X settings I have Prompt me before enabling all
controls with minimal restrictions and unchecked Safe mode (helps limit the
control's access to your computer)

Any help with this roadblock would be greatly appreciated.