This came in to webmaster, i.e. I don't have the machine with the
problem and cannot test it.  Two different people reported the
same thing.  One of them was able to get things working by running as Admin. The other was not.  He was able to get things working by
running in compatibility mode.  When he reached that error, he got
a popup, and the popup asked if he wanted to troubleshoot.  He said
yes.  Then things silently ran, the installation suceeded and nothing
was mentioned that needed troubleshooting.

Thought you would like to know.

I doubt there's much we can do without access to the OPs, but at least we can make sure the windows devs are aware and let them close it (I added the 'windows' component, which will auto-nosy them).

Sorry that I forgot to add the 'windows'.  It may be that there is nothing left to do but close this, however, one of the 2 that mailed webmaster looked at the bug tracker for a work-around for his problem -- at least if this happens again the next person will find something.

Arggh!

Components seems to be a radio box here?  As in I can select 
Windows or Installation but not both?  And by selecting installation
again, I killed David's selection of Windows?

Added this to put Windows back, but, well, if this is what we have
it it time to make a small change to the bug tracker ...

No, components is a multiselect.  In my browser that means I hold ctl and click to add a second component, don't know what it looks like your browser.  (I've added installation back.)