Frequently, this happens when a user imports contacts from an external file and doesn't enable auto-enter options during import. The contacts then do not have a required contact ID number and can't be linked to new records in the notes file. If you then add contacts manually to your file, this contact receives a contact ID when the record is created and now you have some contacts (added by hand) where you can add a note and some (imported contacts) where you cannot.
Does that sound like a possible explanation here?
If so, this thread may be helpful:
I'm having the same problem. It isn't a problem with imported records. It's that the "add a note" script doesn't work when the file is published to the web. Since I'm on a 30 day trial and this is a major problem, I won't purchase the software if a solution isn't found.
Thank you for your post.
I just tried it via Instant Web Publishing, and I am able to replicate the problem. I disabled the script step "Freeze Window" in the script "Add a Note", and you can then add a Note.