Vista - executing scripts within a web browser control under the system ac

We have a .Net 2.0 webservice hosted under IIS that converts classic ASP
webpages into image files. When run under the system account, the underlying
web browser control is failing to execute the script that populates the page
with its data (the resulting image contains the static HTML elements, but no
data). Running a command line app, which bypasses webservice wrapper and
calls the conversion code directly, works as expected producing the static
HTML with the dynamic data. However, if the command line app is scheduled to
run using the "at.exe" command under the system account, the conversion
exhibits the same behavior as the webservice, that is, the dynamic data is
missing from the form. This points to a security restriction with executing
scripts within a web browser control under the system account. How do we
remove this restriction (group policy setting, internet setting, etc)?