When I click on a link to a Harvard Library online resource like a journal article or database, I get a "Bad Request" error from the browser stating the request headers are too large.
"Bad Request" errors (see example) are usually caused because the data stored in your browser's cookies have grown too large for the browser to handle loading the resource link. To confirm this is the issue, try loading the same link in an incognito or private browser window -- if that works successfully, then clearing your browser cookies and cache should fix the error in your normal browser window.
Note that you should clear cookies for all time, not just the previous hour/day/etc. If clearing cookies and cache does not solve the problem, please submit a help ticket to LTS Support (below) for further assistance.