Thank you for your post.
The error -2710 appears to be an Applescript error code. Doing a quick internet search for FileMaker error 2710, I found:
Try running the Applescript separately from FileMaker Pro. Do you get the same error?
Actually the script works fine in Apple Script. Apparently what used to come back as error -10000 now returns error -2710, so that's apparently why my script isn't behaving as expected. I just added -2710 to my error checking as if it were the same as -10000 and that seems to have resolved the problem.
Thanks again for your response.