Can you specify the Episerver CMS version you're using? Also, which browser version are you're using?
We have a user with a similar problem - the reason seems to be that this user has selected a somewhat invalid Content project. The user has the same problem on different OS machines. We fixed the problem by deleting the project in tblProject and tblProjectItem.
You can try below options to fix the error if one is failed then try other
<add dependency="CMS" type="Require"/>
2. Add custom error mode in CMS project web.config
3. In my case the issue was related to caching. I have implemented caching delete functionality following the below blog post and solved the error.
I am trying to get into the edit area of episerver (I get a dashboard as the first page after login). But when I click on CMS and then Edit I get the following error message
Something Went Wrong
Error when loading Edit in CMS " Failed loading content with the url/uri: epi.cms.contentdata:///6"\
I am using a mac. Other people can access, with the same credentials, without any problems. It is a pretty recent version of episerver as well.