I have several of the Guidepost books from the series "Tales From Grace Chapel Inn" that I want to post. However, they have no ISBN #. I went to the section for this and tried to post them but hit a problem. All of the ones I want to post are wishlisted, but when I follow the section's instructions and finish, an ISBN number shows up on my bookshelf and it doesn't match any of those wishlisted, even though my book is exactly like some that are wishlisted. What is happening here? I took them off my bookshelf until I find out what I am doing wrong. Thanks for any answers you may have.  

Is it possible the ISBN isn't on the back of the book and there is an ISBN inside the front cover? I've had a few books that didn't have ISBNs where I expected them to be--and they were on the inside front cover or on the page with all the publisher information.

If they have no ISBN, then they cannot be wishlisted, a different print of it is. As mentioned, check to make sure the ISBN in not listed inside the book. If there is no ISBN on the book, you have no choice but to post them as a book with no ISBN. You can then post in the Book Bazaar and/or your siggy line that you have the books listed under another ISBN on your shelf. Some have also tagged the WLed book with something like "similar book under ISBN #123456" or something to point people towards their version.

I don't find any ISBN on back of book or on inside cover. The blurbs on the back do seem to be exactly the same as the ones on my books. I am frustrated.

This might help...

that is odd that there isn't an ISBN on the publising page, but it does happen.

Do any of the WL books have a real ISBN or is it a made up one?  I went and did a search and several of the WL books I pulled up by your title uses a made up ISBN.  So someone is making up the ISBN to put it out there in hopes that someone will come in and do a search and post it.

Someone may tell me that I am wrong, but if the book in in this system and uses a made up ISBN I would post to what is already in the system as long as everything else matches.  Why reinvent the wheel?  Once you post the book it'll show up on your main account page as either a 1 hour buyer's remorse or waiting for them to respond.  You could always PM them and explain the situation.  My guess is that they know that there isn't an ISBN or isn't one available but they want the book.

Most likely the book was posted at one time w/o an ISBN and then someone else added that to their WL not realizing that those 5digit PBS assigned ISBN's are only good for one book. If these are older books that could explain the no ISBN thing as I believe that only became common in the 90's.  I've had several books even from the late 90's that had no ISBN. Also sometimes book clubs w/leave off the ISBN#. 

I would post them w/o the ISBN and then advertise them in the Book Bazaar.  I would also put a blurb in my signature and tag the ones that are WL as another poster suggested.  Go to the ones that are WL and tag it w/"available on PBS w/ISBN#xxx".  Most likely they'll get ordered pretty quickly just from the Books Posted Today thread.  Also PBS sends out an email when another version of a WL book is posted. Although some people (like me) turn this off.  I have that option turned off because I have several audio books on WL that I only want on audio and I was getting 20 emails a day because they are posted in paperback and hardback. 

I also suggest making as many appropriate tags as you can think of for your book.  You can look at Jane's awesome tagging missions for ideas: http://www.paperbackswap.com/forum/topic.php?t=113598&l=25&ls=0#p2266422.  I did this with a non-ISBN book I needed to post and it was requested within a few days.  Since there were copies available of the same book with the ISBN, I think this version just popped up for more readers.  It's late and I've had a glass of wine tonight, so if this is too vague or non-sensical, let me know and I'll try to explain more.  Basically, just tag with lots of info (character's name, genre, location of storyline, etc.) and even if someone from a similar wishlist doesn't request it, likely someone doing a search based on tags will come across your lone version.