I'm betting it was a permissions issue. Formatted under windows it may have preserved it's previous format. For some older phones (or pre-formatted under 2G cards) memory cards were formatted as FAT16, which would mean it couldn't handle longer file name, or doted names. Formatted on the device it would format it as either FAT32 or Ext3 (depending on how you formatted it). Just a guess at this point, but that could have caused what you were seeing.