It's possible your browser security/privacy settings are set too high, and are blocking you(?). I've never gone to the "paranoid" level settings on purpose, so don't have direct experience there.

If you have loaded browser updates recently, some of the recent ones (especially for IE) have changed the "meaning" of the various security/privacy levels. Fewer things are permitted than previously for each given setting. If you were using a fairly "secure" level, you may have been kicked up to something more restrictive than you want. In IE, look in Tools - Internet Options, at the "Security" and "Privacy" tabs. You could try lower levels - you can always set it back if it doesn't help.

(If you haven't downloaded browser updates recently - especially for IE - you should do so, soon. Even if you don't use IE, it's an integral part of Windows, and needs to be kept up to date to keep the hackers at arms length.)

If you have more than one browser, you need a clear setting for which one is the default. If you have two of them competing to be "the main one" they can get in each other's way.

If you've changed anything in the AntiVirus realm, you may have an accidental setting that's blocking copy as a "download," or just taking so long to scan and give permission that the clipboard doesn't get filled.

All just guesses - but the places where I'd poke around first, unless someone comes up with something.

John