I am using version ASP v5.1 enterprise edition.

It works fine for me, my client keeps on getting an error on her browser using the latest I.E.

Would it be a setting in IE or maybe the server that is causing this.

If i lower my security settings in I.E to meduim low or low, i can get the same error.  Only on the Live site, in my testing enviroment (localhost) it works fine 100% of the time.
My client assures me her security seting is on Meduim.