Today when i click the chapter to update the chapters that i have read it wont update. Also it wont let me move read manga to completed, wish list, or on hold. This happened shortly after I emptied my cache and deleted cookies and other site and plug-in data.
I also had a similar problem but it was because java wasn't up to date. I just downloaded and installed the new version and everything went back to normal. If it doesn't work try to reinstall your web browser.
For me it also sometimes happen but only at Firefox. So in firefox sometimes I suffer it, sometimes I dont. But the quick solution for me is by using IE, its never happen. So when in firefox I cant do any, I just open Internet Explorer, and copy paste the address, then do whatever update I wanna do. But still using Firefox to browse around.