Sometimes, when you login to Skype (usually after new release or problem with servers) , you don’t see your contacts or you see few of them but not all of them.
In any problem regarding contacts, you should do the follow:
1.       Logoff Skype.
2.       Open "my computer" and browse  to the following directory:
C:\Documents and Settings\YourUserName\Application Data\Skype
3.       Delete the file called: "shared.XML" or "shares.XML" (depend on version).
4.       Login to Skype