Help please! Menu tabs stopped working, so have new pages!

Hi, and thanks in advance to any help any of you may offer!

I run TheJointBlog.com, and a couple days ago, out of the blue, our tabs stopped working. When they’re clicked on, it says:

“Bad Request

Your browser sent a request that this server could not understand.”

I tried deleting and replacing the tabs, but had no luck.

It’s even weirder when I try to create a new page; when I click “View this Page” from within the dashboard after I publish it, I get the following message:

“Error 404 – Page Not Found

Sorry, I’ve looked everywhere but I can’t find the page you’re looking for.”

But under that message, it says “Suggested results”, and will show the page, but when I click to open it, it loops me back to the same message.

I have Graphene theme, and it (as well as WordPress) is fully updated.

Any help would be MUCH appreciated!

PS: I tried switching themes, but it didn’t help.