The log shows that the issue is in uninstalling the MSI (so, no surprises unfortunately, nothing that would make diagnosing the issue easier than usual). There is a way to obtain the log for uninstalling the MSI (you'd need to ask tech support for the MSI and then run the uninstall from the command line) and maybe that log will show something. It could be though that the problem will be just a bland "EXT.DLL failed to unregister itself" and in order to understand why that happened, we'd need a special logging build.
I'd suggest several things:
* check if the antivirus managed to block the 32-bit version of MANIFOLD.EXE / EXT.DLL that you have installed (antivirus tools routinely harp at 32-bit code which does nothing wrong and is just not in their database of signatures) - if it did, unblock these files and repeat the attempt to uninstall;
* check if you can rollback the machine to a prior state - I understand this sounds painful, but the alternatives are running unsupported tools that will try to clean up the registry, so if you can rollback to a reasonably modern state, I'd try that first.
Finally, as Dimitri says, you may run a portable install of 9 that requires no installation. You won't have the ODBC driver registered automatically (will have to register it manually as explained in the readme file if you need it - and will have to remember to unregister it when switching versions), but that's perhaps tolerable.
You can run the portable install right now, it will co-exist with the existing outdated install of 9 that you have up until you figure out how to uninstall it cleanly.
It is regretful that installation and uninstallation can fail like this, seemingly out of the blue and with no sure prospects of a repair. We do what we can to help avoid such issues. In addition to making portable installation packages, we are simplifying what we do during regular install / uninstall sequences every chance we can.