Hi Chris,
This seems like you do not have all the correct files but some mishmash of versions.
In version 2.2.7.8 all the features were moved out of the core and into the mojoPortal.Features projects. Before this change they got their resource strings for buttons and labels frome Resource.resx. but in the new version they get them from specific files like ContactFormResources.resx and the old keys were removed from Resource.resx. So apparently not all your files got updated. I would replace all the files and watch carefully for any transfer failures and retry until all the files have been replaced to be sure that all the files are up to date.
Hope it helps,
Joe