Many of you are using the cloud based Cricut Design Space software for your HTV designs. One of the many issues with Design Space is the fact it utilizes Flash and there are constant issues of locking up and the message Shockwave not responding.
Some of these issues can be addressed by switching to a better browser for example Chrome or Firefox BUT even these are prone to problems and hang ups.
Chrome for example can end up with multiple installations of the Flash plug-in and this can cause conflicts and random lockups. see here for details on how to check and fix this issue
There are more fixes and things to check TroyTube has a great video on how to resolve Flash errors here: