Is something wrong with the booking engine at the moment?

I'm trying to book EDI-MCO on 18 Oct 10 to 03 Nov 10.

Yesterday it was coming in at about £450 per adult (about £1700 2 adults, 2 children) on an S fare.

However, today it is only showing B fares for the flight. Expert flyer still shows 9 for S as well as most other buckets.

I definately chose the option 'Lowest Available Fare - Most Restrictions'.

Any ideas?