It's the World Cup Dоwnhill and Super Giant Slalom women races from 28th Feb to 1st March as I have read already on this site there are two runs that are closed in Bansko - Tomba & Tadorka - they are the forbidden ones on the piste map http://www.banskoski.com/?page=bansko-live&sub=live-tracks&language=en
The rest of the resort is open as per normal so you'll still get some cracking skiing in, plus with the added atmosphere of the world cup downhill event.
Sorry didn't see that post from Steve C - over to him I guess for confirmation, I just got my info from websites I've been reading and some other posts earlier this month..
if he has already been/is in Bansko at the moment it's better info.
Stew is correct, only 2 slopes closed with a huge grandstand built at the bottom of the Tomba.
The "Sports thingy" mentioned is the biggest winter sports event to ever have been held in Bulgaria and will be televised around the world, so quite a "sports thingy" then
Just wish I was going out this weekend, it may be busy but the conditions are going to be awesome!