re: "I can't reply to a existing post, but I can write a new one."
Has anything on your system changed recently? Is Java running? Does Task Manager show any odd processes running, or unusual numbers of the same processes (especially Java-related processes) running?
I have a similar problem when I use a laptop my office provided me many years ago. It has some security settings that shut down some important browser functions - such as the ability to automatically spawn a new window. That's irritating, but I've gotten used to it.
If all else fails, download a different browser: Mozilla, Chrome or Opera. They each have advantages . . . and idiosyncracies.