[AS][CS5] Photoshop script no longer opening PDFs without prompt

Question

set this_folder to (choose folder with prompt "Pick the folder containing the PDF files to process:" ) as string
tell application "System Events"
    set these_files to every file of folder this_folder
end tell
repeat with i from 1 to the count of these_files
    set this_file to (item i of these_files as alias)
    set this_info to info for this_file
    if visible of this_info is true and alias of this_info is false and name extension of this_info is "pdf" then
        set myFilePath to ((this_folder & name of this_info) as string)
        tell application "Adobe Photoshop CS5.1"
            with timeout of 300 seconds
                open alias myFilePath as PDF with options {class:PDF open options, mode:CMYK, resolution:300, use antialias:true, page:1} showing dialogs never
            end timeout
        end tell
    end if
end repeat
The above was working when I wrote it.
The next time I tried to use it it fails to open the PDF.
What I get:
Error: 8800. General Photoshop error occurred.
This functionality may not be availble in this version of Photoshop. - <no additional information available>
Removing the 'showing dialogs never' causes Photoshop to ask me what files to open and how to handle the PDF.
Changing the tell to say:
tell application "Adobe Acrobat"
open alias myFilePath
end tell
Opens all the PDFs as I expected it to because the file alias is valid. I have appropriate file access.
set this_folder to (choose folder with prompt "Pick the folder containing the PDF files to process:" ) as string
tell application "System Events"
    set these_files to every file of folder this_folder
end tell
repeat with i from 1 to the count of these_files
    set this_file to (item i of these_files as alias)
    set this_info to info for this_file
    if visible of this_info is true and alias of this_info is false and name extension of this_info is "pdf" then
        set myFilePath to alias ((this_folder & name of this_info) as string)
        tell application "Adobe Photoshop CS5.1"
            with timeout of 300 seconds
                open  myFilePath as PDF with options {class:PDF open options, mode:CMYK, resolution:300, use antialias:true, page:1} showing dialogs never
            end timeout
        end tell
    end if
end repeat
Results in an error:
File some object wasn't found
So anyone know what I'm doing wrong?

Answer 1

It may be but I have not been able to figure it out.
Thanks.
Pedro