Fault reading jpgs from Nikon P510

[John Pearson]

When attempting to switch to a directory containing jpgs from a Nikon P510, no thumbnails or file names are displayed. Invoking in a terminal shows this consistent traceback information:
Traceback (most recent call last):
  File "/opt/extras.ubuntu.com/pictag/pictag/PictagWindow.py", line 366, in liststore_fill
    image = PictagImage(img)
  File "/opt/extras.ubuntu.com/pictag/pictag/PictagImage.py", line 59, in __init__
    self.__metadata_longitude_get()
  File "/opt/extras.ubuntu.com/pictag/pictag/PictagImage.py", line 219, in __metadata_longitude_get
    raise Exception("invalid '%s' '%s' in metadata found" % (key_ref, self.__metadata[key_ref]))
Exception: invalid 'Exif.GPSInfo.GPSLongitudeRef' '<Exif.GPSInfo.GPSLongitudeRef [Ascii] = >' in metadata found

The behavior is consistent with images from two different cameras of the same model. The problem does not arise with images from other brands and models of cameras. I am running Ubuntu 12.04 and Pictag 12.07.17.