Front End Editing Issue

[ACE Advocates for Catholic Schools Aceadvoc]

We have recently encountered an issue when trying to edit articles through the front end of our site. We are able to login via the front end, but when we click the "edit" icon for the article it presents us with the following error (or just a white screen when error reporting it set to 0):

Fatal error: Cannot redeclare class ContentModelArticle in (siteroot)/httpdocs/components/com_content/models/article.php on line 20

We reached out to some developers that said it might be an issue with NoNumber Framework, but the folks at NoNumber said it was not and suggested it might be an issue with the Gantry framework, so I wanted to throw this out to the group. 

We then searched through the files on our server that matched 'ContentModelArticle' and came up with the list below:
(site root)/components/com_content/models/form.php:22:class ContentModelForm extends ContentModelArticle
(site root)/components/com_content/models/article.php:19:class ContentModelArticle extends JModelItem
(site root)/administrator/components/com_content/models/feature.php:20:class ContentModelFeature extends ContentModelArticle
(site root)/administrator/components/com_content/models/article.php:21:class ContentModelArticle extends JModelAdmin

We also located a listing of close matches: 

./plugins/system/aclmanager/overrides/com_content/models/articles.php:14:class ContentModelArticles extends ContentModelArticlesCore
./plugins/system/cdscriptegrator/fields/selectarticle/models/articles.php:46:class PlgSystemCdScriptegratorContentModelArticles extends JModelList
./modules/mod_roktabs/helper.php_:15:if(!in_array('ContentModelArticles', get_declared_classes())){
./components/com_content/models/featured.php:21:class ContentModelFeatured extends ContentModelArticles
./components/com_content/models/form.php:22:class ContentModelForm extends ContentModelArticle
./components/com_content/models/articles.php:19:class ContentModelArticles extends JModelList
./components/com_content/models/archive.php:21:class ContentModelArchive extends ContentModelArticles
./components/com_content/models/article.php:19:class ContentModelArticle extends JModelItem
./libraries/legacy/model/list.php:337: // Try to locate the filter form automatically. Example: ContentModelArticles => "filter_articles"
./administrator/components/com_content/models/featured.php:22:class ContentModelFeatured extends ContentModelArticles
./administrator/components/com_content/models/feature.php:20:class ContentModelFeature extends ContentModelArticle
./administrator/components/com_content/models/articles.php:20:class ContentModelArticles extends JModelList
./administrator/components/com_content/models/article.php:21:class ContentModelArticle extends JModelAdmin

Has anyone experienced an error like this before? Any advice you could offer would be greatly appreciated.