I have had that sort of thing happen on a very weak connection. The connection could be weak due to long distance or due to radio interference from another source such as another AP close by using a close channel, a 2.4 GHz cordless phone or a noisy microwave oven. You can try a higher channel on your AP but I have found that some cordless phones obliterate my connection no matter which channel I use and very strange things start to occur.