It's just a temporary problem. It happens to all websites. I'm sure it will work in some minutes.
That will usually happen when a) Your Java has a problem b) A Minecraft Mod was installed incorrectly c) The files of your Minecraft is messed up
It might be a problem with your mouse. Either that or there is a hardware compatibility issue with minecraft.
On a Minecraft server, chat is always on. If one of your friends can't chat, then it is a problem on their end.
My minecraft was working perfectly in 1.2.4 and I tried to install toomanyitems mod. this caused the problem. despite deleting EVERYTHING from the mod and minecraft from my computer the problem persisted, even after reinstalling repeatedly. Do I have a virus?
force update minecraft to clear all your mods then if you want try again.
What do you mean? Minecraft saves automatically all the time, so I don't understand how that can be a problem.
As of right now, being the current version of 1.7.3, that problem does not exist unless you are running a version of Minecraft that is unstable.
Delete your minecraft.jar. It will redownload it, and fix the problem.
only on single player with WOM.
By getting more memory space.
it might be a problem with the dowload try redowloading it. if that dosint work try emailing the website for suport.