Registering oraoledb11.dll works on one machine, fails on identical system

I've been trying for days to solve this problem, but can find no definitive answer.

I have two identical machines, both virtual Windows 2008 servers, one a clone of the other.      We have 64-bit Oracle 11g on both, and a 32-bit client on the original.    I've just installed the 32-bit client on the cloned machine, and de-registered the 64-bit version of ORAOLEDB11.dll.      Now I'm trying to register the 32-bit version, but I get this:

The two machines have this in "properties":

And they have this in v$version:

SQL> select * from v$version;

BANNER

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Oracle Database 11g Release 11.2.0.1.0 - 64bit Production