You can rename a document in the Web interface by right-clicking the document > and choosing "Rename" from the quick menu.
If this action doesn't work and you are redirected to a blank page the first thing that should be tried is clearing all of your web browsers cached data and browsing history. If that doesn't work try disabling your Browser add-ins and retry.
The Add-in Trend Micro Password Manager has been found to be a culprit in causing this problem. Disabling this add-in resolves the issue.