i bought recently a go pro hero 3 black edition. it films 4k cinema. i tried importing to after effects (i use AE CS6) but it only imports as sound, i cant see the footage. also it takes a while to load the file while importing it.
you forgot to mention important parameters of your footage such as a lenght of shoot file and data format. you may want to preconvert it to some other type of data and probably stretch down its size. 4k for ae too many.