The error screen you are describing seems to be the same as the one I have gotten before, when trying to update my profile.
While I do not know for certain, this is what I think is going on:
You have reached the character limit.
I was indeed able to fix this problem by deleting some (arguably) unnecessary text.
The character limit is 8,000. Try copy+pasting your entire About Me into someplace where you can see how many characters there are (such as Google Docs).
Source: Experience and this.