Sounds like a corrupt file to me. The location you are refering to is a temporary place where the power point file you are trying to open is placed when you click "Open" in the file download dialog.
Have you tried downloading the file you want to view again from the original source, saving it to your desktop and then opening it from your desktop. That should work.
Many files are corrupted easily in temporary files places so saving to your desktop and opening is a safer bet.
I have seen errors like this many times, especially in IE7 after clicking "Open" rather than "Save" in the file download dialog.
Hope that helps
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