How many skins have you got open and how much memory do you have?...
I've just been messing with SKS for over an hour, having numerous skins open, making changes, saving, applying etc and cannot reproduce any of the problems noted. However...
I noticed each skin open added 30Mb to memory, and once I had about five skins open just moving the cursor around caused my CPU to get to 50%+. I also note I cannot exclude SKS from being skinned... so maybe this is a WB5 problem with painting the SKS UI???