Your file hardly qualifies as a "large file". Its size is not the issue.
The error message is too vague to be of any help. All it tells you that the failure was due to some program error as opposed to an OS or file corruption or hardware error. Could be a missing support file, a faulty installation of the application, etc.
So how can I found out what the trouble is? I installed this version of Photoshop (CS5 12.1) when I bought my computer two years ago, and this is the first problem I've had saving any kind of file to any kind of file.
I would say something maybe embedded into the pdf that is corrupt. Like a swatch, font, etc. Create a new document, drag your image to the new document, then try saving as pdf. Maybe it will reduce the file size and remove any unused objects, etc. from the document.
Anyway, its just a thought...
I can save the images alone as a .pdf. I can save the text alone as a .pdf. What I CANNOT to is save them both together as a .pdf! WTF????