Nick - that error message most likely means you have the template component tied to a model that doesn’t have opportunities in it. A nice hack for your troubleshooting is to put the merge fields you are trying to pass as URL parameters outslde the HTML code in your template. In this case it might be:
ID = {{{Id}}}
<iframe src="<a target="_blank" rel="nofollow" href="https://apex/YOURURL?id={{{Id}}}&isdtp=mn%22" title="Link httpsccs15visualforcecomapexSpringCM_OpportunityidIdisdtpmn">/apex/YOURURL?id={{{Id}}}&isdtp=mn"</a> width="70%" height="800px" frameborder="false"></iframe>
This way you can make sure your data merges are good before you go on to make sure your VF code is good.
