ASP 0201 Error Invalid Default Script Language

C'mon, with the recent spate of reportings of this error there just has to be
something global causing the errors so many people seem to be experiencing -
a Windows Update perhaps because that's the only change I've made to my
machine between ASP files being servered correctly by my Win XP Pro IIS 5.1
and the ASP 0201 error I'm now getting.

HTML files, images, even server-side JScript works but VBScript produces the
ASP 0201 Invalid Default Script Language.

I'd appreciate it if we skip over the "My First Website" suggestions of
checking the application's "Default ASP Language" field - mine is set
correctly, as it always has been (when it worked before) to VBScript.

I've tried all the following (with no success):

1. Added <% @language="VBScript" %> to the top of the page.
2. Changed the "Default ASP Language" to JScript and back to VBScript.
3. Used regsvr32 to re-register asp.dll, scrrun.dll, et. al.
4. Removed (including the inetsvr folder) and re-installed IIS.
5. Re-installed v5.6 of the VBScript scripting engine.
6. Reset permissions required for IIS5 (as per MS document).
7. Uninstalled all Windows Updates back to the end of August.

The ASP I'm trying hasn't been changed since it worked last (several weeks
ago) and anyway even an ASP file containing NO SCRIPT fails with the ASP 0201
error.

I've tried so much I now get a bit confused but I'm pretty sure when I set
the application's "Default ASP Language" to "JScript" and the ASP page's
<%@language="VBScript"%> that things worked but when I changed the
application's "Default ASP language" back to VBScript I once again got the
ASP 0201 errors. I'd need to confirm if this is so.

Command like .vbs files written in VBScript work fine so VBScript appears to
be installed correctly.

I haven't tried it yet but regardless of the outcome, adding the
IUSR_MACHINENAME to the Administrators group (which seems to have fixed the
issue for some) IS NOT A SOLUTION. It's the anonymous Internet user for God's
sake! I'd have thought this was a no-no for anyone with this problem.

Remember, ASP used to work WITHOUT IUSR_MACHINENAME in the Administrators
group therefore you're simply masking the CAUSE OF THE PROBLEM which is still
very much present.

Please, does anyone have any resolutions that IDENTIFY AND REMOVE the root
cause of the problem?

Thanks

Tom,

Thanks for the input. I had already performed all the actions in the URL you
sent me to no avail but I went through it again, just in case I'd missed
anything but the problem persists.

I can confirm that placing the IUSR_MACHINENAME user in the Administrators
group solves the issue (at the expense of security) but I really don't
understand WHY it should have anything to do with this account.

I didn't think IUSR_MACHINENAME was used for anything except providing a
user account for anonymous access to web content. Usually lack of permissions
on this account leads to 401 or 403 (can't remember which) errors but
removing all permissions to the ASP file in question doesn't alter the ASP
0201 message one bit -- very strange, almost as if the "error" is happening
at the time permissions are checked?

I have run FileMon to see if there are access errors on any files when IUSR
isn't in the Administrators group, but there are no access errors! It seems
to be more fundamental that permissions on a file. I also ran RegMon but
likewise, there were no access errors.