It looks like the FIA has made a late change to the regulations governing testing which is going to have a small impact on Red Bull and Ferrari, and a potentially larger impact on the Lotus and Marussia teams, based on their definition of when the pre-season testing period ends.
What has happened is that somebody has asked for a clarification on article 22.4, part c)
22.4 No track testing may take place :
[...]
c) Between the start of the week preceding the first Event of the Championship and 31 December of the same year with the following exceptions :
Red Bull and Ferrari interpreted that underlined section to mean that testing can take place up until the 12th March, since the race weekend officially starts on Friday 16th March (although, since scruitineering takes place on the 15th, it could be argued that the race weekend effectively starts on Thursday).
However, the FIA's interpretation of that clause is different - they have defined that clause as covering the entire week in which the first race takes place, so they are working backwards from March 12th - going back an additional week, therefore, means that the test restrictions kick in on the 5th March, which was when Red Bull and Ferrari wanted to run their cars.
http://www.autosport.com/news/report.php/id/97713It hasn't had a major impact on Ferrari or Red Bull, although it has caused them a slight logistical issue since both teams originally assumed they'd have 24 hours more than they now have. Lotus, however, will take a larger hit - after going to the effort of getting permission from the teams to carry out a one day private test after withdrawing from the first Barcelona test, they are now unlikely to be able to use that extra day as their one day test seems to have been scheduled for after the 5th March.
Marussia, meanwhile, are now effectively barred from testing - they might be able to use up one of their four days of permitted straight line tests or use up their limited mileage for promotional material, but they won't have a chance to see how their car behaves on a 2012 specification tyre until FP1 in Australia.