I've now taken a look at the exif data with a better viewer and the actual equivalent focal length is 154mm moving the rule-of-thumb minimum shutter speed up about 1/3d stop to 1/38th sec. The rule of thumb assumes a truly stationary subject which the dog probably was not.
The other factor that may be affecting this particular photo is focus. At 154mm focal length the minimum focusing distance will be about 28.3" (2.36') in normal mode. Judging from the size of the dog's head in the photo you may well have been closer than camera will focus in normal mode at that focal length. If you can remember the details of that shot you can judge whether that was the case or not.
While I would still like to see another blurry photo to see how many of these same factors are present I think you should do the formal tests suggested by Bailey59 and post the results.