I am really getting pissed.  Every one of the fonts I am opening up are getting certain blocks substituted, all the time.

Not only do I not understand how this is happening, I don't understand how to fix it.  If you could see my blocks, I took very special care to get them in an order that was much less confusing than the layout.  So that when I needed a certain block that I could find it easily.

But, not only is the tip of the 2 block angle block replaced with an F'n square block (in the M, for example), the layout of the used blocks is all F'ed up.  How the hell does that happen?  If I drag the right block over the used set and drop it on the big square block that F'ed-up the whole F'ing mess, it does NOT replace it (and all occurances of it).

So now, the only way to work with it is fix the stupid blocks manually and use an F'ed-up used block layout that I painstakingly tried to get right specifically for this project?   

I never have multiple browsers open for the same font.  Rarely do I have multiple fontstruct editor windows open, and only then in order to copy blocks or block sets, so only briefly.  I do often have to fontstruct website windows open, but not editors (except in the infrequent instances mentioned).

Trying @Zephran's trick, now.

"Then drag your angled block over THAT, and it should get replaced."

Dragged the square (standard first) block over it.  The block was outlined in blue as I did it.  When I drag the angled block I want then, over that one, in the used block section (like before), no blue outline.  Letting go of the mouse button and dropping it there, nothing happens.  I use the mouse wheel to zoom in and out and nothing happens.

You know, this has been happening so much lately.  There are too many issues now.  I like the idea behind building fonts, but without a larger set of circles/spheres/curves I have pretty much run the gambit of what I can use FontStruct for, blocky or angled fonts. 

I actually setup a number of fonts that I would pusue the designs I wanted to do that would fit in that mold, and I have been trying to do or finish them.  But after that, I will probably be running out of ideas, anyway.

Don't get me wrong, the list of projects I have going on in here is quite long.  And I noticed some mistakes in the fonts I am making, so I would like to remake them, but I am determined to finish the font project I am working on before, and then add the correction to the same general font family. 

But now, I am getting afraid to update any of my fonts under the assumption that the whole font project (not just this font, but any derivative font thereafter) would get destroyed.  I just do not like how the blocks are laid-out, it makes no sense, and getting them placed right takes forever.  To not have them placed right is akin to a poor UI.  And an even more poor user experience.

I waited a long time.  By now I had been avoiding coming here to kill sparetime enough so that I installed debian linux on my old laptop that wouldn't reliably run Windows 7. Thankfully, debian linux runs great on this laptop, not a single abrubt system crash (and it's an i3 so has some snap) like with Windows 7 Home Premium or Ultra.

Anyway, logged in, loaded the font into the editor and had to turn expert mode on, and then I was able to replace that one block, which replaced all instances of it with what was there in the first place.

Issue resolved. 

Previously it was just the upper & lower cases, as well as the numerals.  Added whatever punctuation and symbols.  I still have to tackle (parenthsese), @, [], {}, ^, _, <>, ? and possibly some others just to finish off Basic Latin.

What's there now has been kerned.  Added ( ) _ [ ] < > ? and I will leave it there for now (unless anyone has a character request, I'll add an @ eventually, otherwise this is a decent basic character set.

Right-o.  Done!  Thanks.  ;)

Thanks, @zephram.  This was another let's see if I can... fonts.  ;)