Has the new filter (display_featured_image_large_image_size) been implemented and, if so, do you have sample code to change the custom size?
No. The issue was resolved by deactivating the NextGEN Optimizer plug-in that had also been installed.
You have to turn off the “Organize my uploads into month- and year-based folders” setting in the “Miscellaneous Settings” section of your blog. Once you upload your logo you can turn this function back on.
That is correct. I am running v2.7.1 of WordPress and have the plugin successfully running on two other blogs running the same version.