have you allowed the apropriate filetypes to be shared ?
To check this go to library and right click on your shared folder(s) and go down to filetypes here you can tick any type of files you wish to share
if these are all ok try unshareing your folder and then reloading it to your library
if these things do not help post back here giving details of your pc set up .... operating system/firewall/modem or router model/which winmx you are using & isp.....im sure someone will be able to advise you of the course of action you need to take
