Maybe I read wrong (only that no error in gimp console )
Just to confirm :
Filters -> Python-Fu -> Console (paste the code and enter) - no error?

exactly
I copied the list of statements you provided to me, opened python console, entered the full list of statements and everything worked OK, result (i.e. what I see on my python console) is as you indicate (which shows I have python 2.7.5)

to complete the info on the error I get:
just this generic one:
GIMP Error
Plug-in crashed: "Selector.py"
(C:\Users\User\.gimp-2.8\plug-ins\Selector.py)

The dying plug-in may have messed up GIMP's internal state. You may want to save your images and restart GIMP to be on the safe side.

only to let know a follow-on on my trials
I have on a USB pendrive an OnkelHatti Gimp (2.8.11)
I added there those two files related to Selector into the plug-ins folder (plus the required entries for glade under Gimp bin); the plug-ins folder there was empty (so, no conflict -maybe- with other python plug-ins, like it could be the case on my primary Gimp, full of plug-ins)
I got exactly the same error.
Just to check, I added two other python plug-ins requiring glade: LineBorder2 and Indexprint: both run perfectly, as in my primary Gimp
All Berthold Hinz plug-ins using python+glade do not run on my PC...
(if I remember correctly, also Rod did not succeed making them run)

To try to solve the problem - I installed Gimp 2.8.10 again (to compare files - and look what possibly the lack of a standard installation ?)
And what's the result?
Only added the file libglade-2.0-0.dll (in the catalog - bin) - Adagio Selector works well - is not that strange ?

you mean:
- added Selector.py and selector.gui to .gimp-2.8/plug-ins
- added libglade-2.0-0.dll to gimp/bin?
and no other additions?
nothing added to python/site-packages?

it's strange, as you say...

MareroQ, do you have (and running) all Berthold Hinz plug-ins using python+glade?
I mean especially DRITool
(Selective Brightness works!)

Everything as written.
In a clean install - only added libglade-2.0-0.dll and I can run all the plugins Berthold Hinz.
DRI probably not work very well - but that's another issue - it requires longer test

OK.
Tomorrow I'll try to do as you did.
Hope I'm lucky, this time...
Good night! and many thanks for your support...

@MareroQ
Good morning.
I did what you did yesterday:
- new clean installation of Gimp 2.8.10
- addition of Bertold Hinz plug-ins in plug-ins folder
- addition of libglade 2.0-0.dll to Gimp 2/bin
results: still the same as in my previous installation: crash on Selector (DRITools does not show up)
At this point I'm almost sure it has to do with something in my Windows/System 32, but I'm not on the way to reinstall Windows and going thru the over 6000 elements in there to find out which one I put there (following instructions for some other plug-in, very likely) is a "mission impossible".
So, I have to give up...
Thanks for your help.

a new update in my endless story..
I had the opportunity to send the 3 components I have here (selector.gui, Selector.py, libglade 2.0-0.dll) to another gimp installation on another PC running Windows 7 (but 64-bits). There I moved the two components of the plug-in in the plug-ins folder, the dll into Gimp 2/32/bin (being there the system a 64-bits one) and I got the same error! So it's not my Windows/System 32 the responsible.
Is it possible that the versions of my two components (which -I'm sure- I downloaded from the site originally linked by PhotoComix in its initial post) are incorrect?
Could you -please- post here your running copies? I will substitute myne and try again...thanks

Here are my selector files and the libglade if You want to test. I also installed other Ryadagio plugins and LineBorder 2.4.2 and they work too.

thanks Nidhogg.
Downloaded and replaced all components, but no luck.
It must be...my presence in front of the PC!!!