This was posted on another forum last week:
Mine has started acting very flakey... It will mount and unmount randomly and then disappears all together for a while. I called Samsung today and was told to reset my phone and that there is no reported problem.... blah blah blah. I then went to best buy to talk to them who informed that that I can exchange my phone but there is no point as they have had lots exchanged for the same issue and that it will happen again. The guy told me that one customer exchanged his phone 3 times in 2 months and it happened to each phone after a period of time.