Problem while installing MiKTeX 5.1 in Windows

Question

I have been a user of MiKTeX (mostly using LyX to typeset my documents with the help of MiKTeX). Till now, I was using MiKTeX version 4.2 to do my work, and I decided to update it to the newest version of MiKTeX available (version 5.1). After uninstalling the previous version, I downloaded the files to my local machine and proceeded with the installation. However, just before the installation was supposed to start, I get this error:

Usage: setupwiz [OPTIONS]
Options: 
--allow-unattended-reboot
--auto-install=yes
--auto-install=no
--auto-install=ask
--common-config=DIR
--common-data=DIR
--common-install=DIR
--common-roots=DIRS
--download-only
--dry-run
--help
--install-from-local-repository
--local-package-repository= DIR
--no-additional-roots
--no-registry
--package-set=SET
--paper-size=A4
--paper-size= Letter
--portable[=DIR]
--private
--program-folder=NAME
--remote-package-repository=URL
--shared
--unattended
--user-config=DIR
--user-data=DIR
--user-install=DIR
--user-roots=DIRS 
setupwiz reads its arguments from setupwiz.opt, if such a file exists. See the MiKTeX Manual for more information.

Now, after this, there's only one 'OK' button, which closes the dialogue box. Nothing happens after that. I looked up the MiKTeX Manual as mentioned in the error message, but couldn't understand the error. I am further attaching the screenshot of the error dialogue box for additional information.

I will be very grateful if someone pointed out what is the matter with this installation.

P.S.: As MiKTeX is a very essential tool for my workflow, I reinstalled version 4.2 on my computer but didn't come across any such issues this time.