Running Norton Internet Security, perchance? This is a very intrusive program, and interferes with the RenderCow function even it you tell it not to. Also, what OS and version are you using? There are a couple of MS dll's that have to be updated (or installed to begin with) to the latest version before the Cow's will behave. I get all the needed files when I install Visual C++6 (the release version), so that is the cluster of files you need to check into; the VC++ runtime should do the job. On VuePro, have the ProCows been updated? That is the first thing that should occur when a Cow is contacted, and there has been a version upgrade in VuePro (you would get the update bar window on the Cow computer desktop). The Cows are nothing more than the actual render engine with a TCP-IP front end instead of a GUI; if the engine version numbers do not match, you will either get a lockup of the Cow, requiring a shutdown, or an error state that causes VuePro to CTD.