Formatted Search error with a different user

I created an add-on form and assigned formatted search to some of the fields.

When I logged in with a different user(<b>test</b>) and tried to use the FS via Shift+F2, I received an error saying "You're not permitted to define recurring postings".

I gave that user the authentication for recurring postings, but now I receive an unclear error when I try to use the FS on the same editbox:

"<b>You are not permitted to perform this action</b>."

<b>Any ideas</b> ? What may be the reason for that unclear error message ?

<u><b>Note:</b></u>

<i>After logging on with the same test user, when I try Shift+F2 on another editbox (which is normally not assigned a FS) it works normally and I can do all FS operations like assigning a new FS, etc.</i>