This JIRA instance has been upgraded from 6.4 > 7.0 > 7.x Latest.
The homepage displays the following error : 
Searching for this error led me to the Atlassian forums, which suggested I rebuild the index. This was done, but did not resolve the issue above. Further searching on the forums led me to a topic that indicated it was an issue with the application indexes.
I moved the home/caches/indexes folder and attempted to reindex but got a few new errors.
In the GUI itself : "A task could not be found for the given task id"
In the application log :
Error creating bean with name 'com.atlassian.jira.toolkit.customfield.searchers.DomainSearcher': Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.atlassian.jira.toolkit.customfield.searchers.DomainSearcher]: Constructor threw exception; nested exception is java.lang.NoSuchMethodError: com.atlassian.jira.issue.customfields.searchers.ExactTextSearcher.<init>(Lcom/atlassian/jira/jql/operand/JqlOperandResolver;Lcom/atlassian/jira/issue/customfields/searchers/transformer/CustomFieldInputHelper;)V
Any ideas?