when you kill someone and get 3 or more levels, it will open up multiple spendskills windows. you can tell because it will say pending(5) at the bottom. only problem is for some reason after you click 2 or 3 skills, adn cancel out that number of spendskills tabs, they all exit out. so you have to type spendskills again, or wait until you get only one or two levels.
a way to fix it would be to wait 5 or so seconds after you get a level to allow all of them to be processed, so when it pops up there is nothing "pending"