I've noticed that my 2 month old black Macbook is losing charge extremely quickly while asleep (when I've finished using the computer I simply close the lid). For example, before I went for my dinner tonight I had charge of approx 50%. When I returned 30 mins later it was down to 35%. My computer usually hold its charge pretty well with around 4 hours, so I'm quite mystified. Has anybody else experienced this problem?