It seems that the polish version you're using does some editing to the UI files. Use Near Infinity to extract the original Polish UI files and post them here. The two files you're looking for are STMOS.mos and CGMOSM.mos. Also look into the Override folder and find the same two files (The ones my UI uses). Post all 4 files here so I can check them out.
Okay, here they are - both original Polish and those from Override.
If you have installed Qwinn's fixpack or tweakspack it may have something to do with it, because I think they do some tweaks in this department.
No, I'm not using any of those (and haven't even heard about them). Although it seems that this change might be a fault of widescreen mod, as without your UI fix, the short-cuts are still in English. Since widescreen mod itself changes only the resolution, not UI (although I can't understand why he's changing those short-cuts in this case), I hoped that perhaps your tweak would contain an optional fix for this little issue. Can I ask for adding this, please? As long as it's not a problem.