Weird caps lock problem on log in screen

Hi,

I just bought a brand new MacBook Pro 13 inches (2015). It runs Yosemite (10.10.3). Everything looked perfectly fine until I shut it down after using it for the first time; when I fired it back on, I could not log in even if I knew I had the right password (I had just changed it). I soon noticed that, on the log in screen - and this only happens on the log in screen - the small icon that indicates that the caps lock is on does not follow what the light on the keyboard indicates. This was what caused my password problem; when I type it using shift for the caps, I don't have any problem. Does anyone have encountered a similar problem? I don't think it's an hardware issue since I made several tests and noticed that it only happened when trying to log in immediately after booting (and not after waking the computer or when using any app whatsoever). What could cause this? Is there a setting somewhere that could solve it?

Thank you very much!