Error when trying to create a server object in Classic ASP - asp-classic

Question

The .dll is ASPCache_x64.dll, in C:\Windows\System32 (I know; this decision was made before my time.)
The server is a Windows Server 2008 R2 VirtualBox VM with IIS 7.5, on a host running Windows 7. The website in question is a classic ASP site running under .NET Framework 2.0. The VM itself is a copy of a VM we use as a template, and no one else using a copy of that machine is having this problem.
The problem:
On loading any page, I get the following error:
ERROR IN PROCESSING: ?
ASP Code:
Number: 0
Source:
Line
Number: 0
Description: Create object failed
ASP Description: An error occurred while creating object 'myCache'.
Other information:
eventually traced to Global.asa <object> tag
attempting to create and use an ASPCache object in a VBScript file run from a desktop folder works fine
attempting to create and use an ASPCache object on a test ASP page in the same domain gives me the same error until I refresh the page, at which point I get this error:
(workaround for broken markdown; ignore this line)
ERROR IN PROCESSING: /test_createobject.asp
ASP Code:
Number: -2146959359
Source:
Line Number: 4
Description: Cannot create ASPCache object - a required component is missing. Please reinstall your software.
I have tried:
downloading a fresh copy of the VM
making sure IUSR has read and execute permissions on C:\Windows\Systeme32\ASPCache-x64.dll
de-registering and re-registering C:\Windows\Systeme32\ASPCache-x64.dll with regsvr32.exe
granting IUSR read permission on the ASPCache and ASPCache.1 registry keys
applying the fix found here: Server.CreateObject Failed in Classic ASP
checking every setting I can think of against our shared dev environment, which doesn't have this problem
restarting IIS after every change
restarting the computer after all of the above
granting individual app pools read and execute permissions on C:\Windows\Systeme32\ASPCache-x64.dll
changing the default application pool identity to NetworkService
changing the default application pool identity to [Machine name]\Administrator
I've been Googling this problem on and off for months. Nothing I've found has helped.
Code for the test asp page, which doesn't work:
<%
Dim testCache
Set testCache = Server.CreateObject("ASPCache")
testCache("Marco") = "Polo"
Response.Write testCache("Marco")
%>
Code for the VB Script, which does work:
Dim testCache
Set testCache = CreateObject("ASPCache")
testCache("Marco") = "Polo"
WScript.echo o("Marco")
Relevant code in Global.asa, which gives the original error:
<OBJECT RUNAT=Server SCOPE=Application ID=TestCache PROGID=ASPCache></OBJECT>