I had the same problem, except my skype was freezing up even more then what you said and I found something on the net that worked for me.
Here is what I did and it definitely fixed by scenario, I was on windows 10 but it may not matter:
1) Go into control panel
2) Go to network and internet, then internet options
3) Then click the security tab, and then the restricted sites icon.
4) Click the sites button
5) Then put in https://apps.skype.com and add to the list.
6) Close and reopen skype when done