I was getting the error
E576: viminfo: Missing '>' in line: [file names] about ten times with various file names whenever I opened or saved a buffer in Vim. This happened both in normal vim and with MacVim. This was followed by the line
E136: viminfo: Too many errors, skipping rest of file. Other than these obnoxious messages, Vim itself worked fine.
To fix it, I opened
~/.viminfo and deleted everything in the section labeled
# History of marks within files (newest to oldest):. I lost all my history of marks within files, but that was acceptable for me since I was starting a new coding session for the day.
So far, I'm not sure how my viminfo got into this state.