problems downloading Kindle books
I have owned my Kindle paperwhite for a year but I have recently started having problems downloading books. In the past I have always downloaded books to my Mac and then transferred to my Kindle via usb. However, in the past month or so some books download properly, but some do not. When the books download properly they have a .awz file name, e.g. Alice in Wonderland.awz but for the books that don't download, they either just download as FSDownload (no title at all) or sometimes the title of the book but no .awz e.g. just as Alice in Wonderland.
I suspect it might have something to do with my software because when I tried downloading the same books on a PC, they showed up fine with the .awz file. I think this problem coincides with when I installed Mavericks.
I have contacted Amazon customer service and we tried all sorts of things and none of them worked. Finally, the customer service people suggested I try here.
Any help would be greatly appreciated.
Thanks.
OS X Mavericks (10.9.2)