On my blog The Growing Vine, http://www.thegrowingvine.com, I use Posts and Custom Post Types. The tag links on my posts work fine. But, the tags on my CPT sometimes result in a 'Page not Found' error.
An example CPT page is: http://www.thegrowingvine.com/Recipes/raspberry-filled-crepes/
If you click on a tag you will see the link is broken. I use Custom permalinks /%postname%/. I have not set a Category or Tag base in permalinks.
Thank you for any help on this! Nancy