FYI, The pdf format that's referred to in the error message points to the file you're trying to save, and has nothing to do with Acrobat, or even trying to save as a pdf. As you may (or I suppose may not, judging from all the posts in this thread) know, pdf is the native format that Illustrator has been using since version 9. This is also why you can open most native Illustrator files in Acrobat Reader simply by changing the file extension to pdf.
So, don't look into Acrobat related issues any more to tackle this issue, but rather try copying and pasting the file content into a fresh Illustrator document, and save that. The pdf/difficulties thing will come up from time to time, and is usually an indication there's some type of corruption in the file. Those are the breaks.
Bert