There are several problem that cause your pc freezes when using Instant Messaging, like facebook, skype,etc.
1 Badly Fragmented Hard Drive
system fragmentation is one of the solution for freezing when making video call.
Select my computer
right click your hard drive
navigate to the bottom , where you see properties-click that
move over to the tool tab
select Defragment Now- optimize
2 too much ram and CPU usage consumed or some time too much disk space occupied
when making video calls, especially the high power consumption ones like Skype and oovoo, you CPU will tend to overheat rapidly than normal.
To limit or reduces the CPU AND RAM intensity .Go to
Go to task manager
close all the things that are running in the background that is causing the the high cpu usage ram and full disk space.Normally Antiviruses tend to consumed much of the Disk space.
3 Un-updated version of your video call software can cause your pc to freeze, try and update it or reinstall it..also, if you are using a laptop make sure the power plan is on balanced or high performance .Having the power plan on Power saver may reduces your computer performance ,hence causes lagging.