[This is not a question but a tip to hopefully save someone else the time it took me to trouble shoot this issue].
When saving a template in PowerPoint 2007 you can choose to save as a PowerPoint 2007 template or one compatible with earlier versions. If you chose to save a PowerPoint 2007 template, make sure that you have changed the compatibility Save files in this format option (see Options | Save tab) to PowerPoint Presentation instead of PowerPoint 97-2003 presentation.
If you do not, and if you are storing your template in a workgroup file location, you will not be able to create a new PowerPoint presentation based on this template because PowerPoint will not recognize it. BTW - this problem does not exist for Word 2007 or Excel 2007.