Well, to be honest I solved it somehow, but why exactly it broke down is still a mystery for me. I depend heavily for Python in my projects, so I do most stuff with it.
First, even a simple script like: Function.Call("my_function",0) didn't work in a new , empty project (aside for the function plugin). Then I reinstalled CC, same problem but NOT with this new, empty project. So I downloaded Python 2.6 and manually copied the StrinIO.pyc into CC Data folder. Well... that didn't help.
But what did was deleting all other StringIO.pyc from other locations - it seems that in desperation I copied that file into the project folder and it was a 2.7 version. After deleting it, and tweaking the code - so I deleted all the in-developement parts and left only those that I knew would work - I could resume coding again.
I posted all this for anybody in the future with the same problem. Oh, and Jayjay, I didn't try exporting the game yet. That would test something, out of curiosity?