Ask HN: What tech I should use to make an ERP?

I want to write a new ERP from scratch, my current one was made using PHP-GTK and MySQL, because GTK3 policy of changing the API a bit too fast, updating it became a problem.

Also I found PHP to be problematic, introducing some bizarre bugs because of esoteric reasons of how it works compared to other languages (like... checking if a text box is empty returning true if the contents is "0" but not if the contents are "0.0", I noticed that when I saw lots of entries in my database was 1, or 0.0, when the user wanted it to be 0 and the program blocked them).

If was SOLELY up to me, I would use C++ (or pure C if possible) and Qt, and maybe keep the MySQL... But the other coder wants to use languages that I don't know how else to describe other than saying it is "modern", where the language do some things for you.

So I need suggestions of what technologies to use.

One big constraint: the thing need to be absolutely reliable, I am from Brazil, and here is mandatory to send electronic documents to the government every time you make any sale, meaning whenever the program stops working, it means you can't sell anything, thus blocking the whole company from operating.

Another constraint: I should be able to easily make a organized interface with tons of information, the government documents require a ridiculous amounts of fields, some of them rather complicated (we have the dubious honor of having the most complicated tax code of the planet, according to the "Ease To Do Business" ranking), and they change a lot, one of the reasons GTK is currently in use is because of Glade, its editor, that allow quick hacks whenever the government change suddenly what fields it wants in your documents.