virtualbox.org

No end of trouble with v2.1 release; I have lost all of my .VDI files through corruption of v2.1.

I was unable to back-out to 2.0.4 which I was happy with - no end of errors with that. So in the end I stuck with v2.1

I recreated all my new .VDI files painstakingly, took all day to wait for WinXP etc. to reinstall.

Now vboxmanage.exe clonehd, consistantly creates a corrupt clone every single time.

This is what I installed VirtualBox-2.1.0-41146-Win_amd64.msi

Is this release VirtualBox-2.1.0-41146-Win_amd64 an alpha?

No, but .0 releases are known to be not the most stable releases. If you want to clone your VDI file, use the normal file copy of your OS and use the undocumented command vboxmange internalcommands setuuid <filename>. Exact command might be different. It's mentioned here several times. See the Tutorial: All about VDIs too.