Yeah either bad apps or bad phone... try a factory reset I guess, pull battery and then try it. The only thing a faster sd card will help you with is if you have large video files or lots and lots of pictures and of course transferring will be much much quicker. it won't really have much impact, just small stuff. saving photos, recording video... about it really. Maybe if you had a game or something that had large amounts of data stored on the sd card it used..? i dunno.