This can be an especially annoying error message as it does not help you much where the error is. Normally this error occurs in the case that a snippet template that is included in a slot has an error. There is no indication though which one is at fault and it may be a slot within a slot.
The first thing to try is to go to the Active Assembly Table editor to see the contents of all the slots. You can then click on each of the links to preview the snippets for each relationship. You will normally then find the one that is throwing the error, once you resolve the error (you should see the error message) in the snippet template or remove the item the page should render fine. If one of the items also has the same Transaction rolled back issue, you want to start the process again on that item/template.
This can get a little more difficult though if the item at error is being pulled in by an auto slot or the velocity code is overriding the template being rendered and only that template is at error. In this case you may need to comment out the slot in the template to work out which one is at fault.
The error is sometimes from a link in navigation. If this is the case you may need to preview each template of the Navon to see which one is at fault and then go through each landing page link to see which is at fault. This may be be difficult for complex navigations, e.g. for a breadcrumb it may be one of the ancestor landing pages is breaking.
Hopefully you have the simple case of a regular slot you can diagnose with the Table Editor.
This has been resolved and will be rolled into CMSystem 7.2. With the fix it will be a lot easier to see which template/content id/slot is failing. Errors will be shown in preview in the context of the page, but will prevent the page from successfully publishing…