You are getting a memory error when processing the portrait image. I do not know what about portrait images would cause the processing to take more memory than the landscape ones, but using the trouble shooting guide article 25 you will see the error:
`
Fatal error: Allowed memory size of 100663296 bytes exhausted (tried to allocate 11392
bytes) in /home/content/c/o/w/cowleycrawford/html/album/zp-core/lib-GD.php on line 296
`
Your image filesize is 2.5 megabytes which is pretty big for WEB applications. However, it is not the file size that matters it is the image dimensions and the memory it takes to process the image. You might try disabling auto-rotation. Rotating an image will take more memory. So, specially if you think the image does not need to be rotated by Zenphoto that might be a work-a-round.
Also look at the articles above #25 in the guide for more information on images that are too large to process.