Help Samsung galaxy ace refusing to update software version?


Samsung Galaxy Ace refusing to update software? (Gingerbread) 2.3.6Hello

I'm trying to update from software version 2.3.6, but after tapping 'check for update' I'm almost immediately greeted with a 'connection failed' message, despite the fact I have 3 out of four bars and internet works fine.
When I then try to update over wifi, my phone still tries to use 3G. (And still fails update.)
My phone isn't rooted or anything like that, and my sister who owns the exact same model had no problems.

Any ideas are much appreciated

Happy new year :)