Sometimes, when you save your Site as a Template, you get a .stp file and then when you try and create a new site out of it, it could give you a Site Template Invalid or not found issue....



This usually is because your Site Template has got dependencies (features) which are not correctly present ie installed.



The best way to see this is to use STP Inspector tool (http://stpinspector.codeplex.com/releases/view/38429) which will show you the various dependencies and then you can independently go and troubleshoot them.



Once you correctly install all dependencies, the site template will start working correctly.