Thanks to PeterK (who's currently blog-less) I finally solved another software related mystery. Since lately my Excel has been acting strange - keyboard shortcuts were not working or were doing completely wrong things. Ctrl + C, for example was trying to add new rows etc.
I was very troubled since there is no way (or I can't find it!) to customize and see keyboard shortcuts as we are used to from older version of Office and other MS programs live Visual Studio.
Running Excel with command line parameter /S (as in "Safe Mode") solved the thing.
There is even MS knowledge base article about it Description of the Excel 2007 hotfix package: March 7, 2008, but the hot-fix is not easily downloadable.