Problem on Vista with Microsoft Office Web Access

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I just bought a new home computer that has the Microsoft Vista system. I can access/view my work emails via Microsoft Office Web Access, but I am unable to send any new emails or reply to any emails. When I try to do either, I get an error message that "Windows is shutting down" and finally to a message about DEP security settings.

I've called our tech support folks and they haven't been able to help thus far. Any suggestions on how this problem may be solved? 'Would greatly appreciate any help. Thanks!