If you have problems please file a bug report and provide all the information requested by the guidelines. It is usually impossible for us to investigate any reports without that, so as this post stands, nothing will be done or even looked at.
BTW it's actually best to use just under a power-of-two size for Sprites - since spritesheeting on export assembles everything on to a power-of-two texture with 1px border padding around it, then the ideal size is two pixels less than a power of two size (e.g. 30x30, 62x62, 126x126...). In fact I would just ignore the size and let spritesheeting do its thing.