This problem can occur with multiple versions of Snagit. Changes were made in Snagit 11 to help with this problem but it does not resolve the problem on every machine.
If you are using a Dell printer, we have had reports from users that installing the Dell Open Printer Driver resolves the issue. That can be found here.
Another option that can help is click on Tools > Program Preferences > Program Options an unchecking the box for "Always keep Editor running in the background". Then see if the same problem happens after restarting the machine.