Files in certain shared folders not visible through network

This is a problem that occured on my computer once before and i fixed it, but now i cant remember how i fixed it.

Basically, i have one shared folder on my computer that people on my LAN in college can access. Inside this folder there are 6 subfolders, each containing certain files (Avi's, Mp3's and text files). However when accessing the folders through the network, only two of them seem to be containing files. The rest appear empty, even though when i check the directorys on my computer i can see them.So in short, some folders are fine, and others appear empty even though they contain files.

I am pretty sure that it is a windows update Hotfix that is causing this problem, as i'm almost sure i had to re-install a hotfix last time to fix it. The problem is i dont know which hotfix it is and i am having trouble finding any information on the internet. Any help would be greatly appreciated.