Runescape refuses my Username and Password! Why?? ?

I go to Runescape.com, click Existing User, Click "Choose Best World for Me", I get to the setting options page where they start playing the cheesy music, and I click 'Log In'.

I type in my Username.

Type in my password.

Then it says "Performing Login..." And I'm all filled with hope!

Then it says "Invalid username or password. If you have forgotten your password, click here."

I hadn't played my runescape for about half a year until last week. I clicked that I forgot my password, then I remembered it without the help of the website, wrote it down, and logged in and played runescape 3 days in a row (not day and night!) with out any trouble.

Then, on the fourth day, it wouldn't let me login until i tried about 5 times in a row. I used the same username and password each time, because I knew they were the right ones. On the fourth time it finally logged in.

Then I didn't play for about 5 days. And now, since Wednesday, IT WON'T LET ME LOG IN!! It says the same "Invalid Username or Password" each time I try to login!! And I'm not misspelling anything, and I'm not using the wrong passwords or usernames.

Has this happened to anyone else?

Or can anyone help me or think of something I can do?

I mean my character was only on Level 7... but idk. I don't want to start all over again.