Ok. There is something related to the project here. I made a rollback to an erlier state, from almost a month ago, when I was working on a project with AHMI without issues. Tested the latest version 3.6.6 and still the same error! Just unziped the project, deleted obj and bin folders, and rebuilt. Same error.
But without being sure that could be my framework installation, I just launched the project I was working on at that time who has AHMI v3.6.2... and it worked flawlessly! I said earlier that I tested this version, but it was a zipped backup file that I downloaded at the time it was the latest version, so it was the original project from your webpage.
Here is the strange thing: those original file backups that I downloaded and keep as version history and I try to open generate all this error when hitting rebuild solution, as none of them would show the controls on the toolbar. But older projects I have that were already built, I can see the controls and insert them as normally you should be able. Just rebuilt that project, and failed the same way for the first time. Deleted that unziped again and hot rebuilt, and the project kept working fine including control insertion (random?).
I'm going to keep trying and rollback to a really earlier state, just to be sure if is an installation problem. If not, well, I'm really clueless. Only thing I can imagine to is to reuse the project I found that worked and stick with it until I have time to reinstall everything, even OS, hoping that will not get "corrupted" in the meanwhile.
So any other suggestion to try to find a fix, is welcome.