Blame MageUK. Always blame MageUK. You've cleared your cache, but you haven't cleared your cookies for Tip.It. We had a problem with users in the past - limits like max cookie size, max cookies per domain, etc. Overtime, these limits get reached. This is the reason we're switching to local storage (and the reason you're getting a bad request) - which you'll see soon (is already implemented on pages such as the Ports Timer). If you haven't cleared them, try. Chrome: Tools > Clear browsing data... (Or just Ctrl-Shift-Delete) > Delete cookies and other site and plug-in data Firefox: Tools > Options > Privacy > Cookies > Show Cookies Internet Explorer: Tools > Delete Browsing History > Cookies