computer locked

when I turned my computer on this morning I got the message that my computer was locked. It asked my to input user and password, which I did, but it told me the information was incorrect. I phoned the place where I purchased my computer and was told to press <enter> which I did, and the message went away and everything was ok. I was told that if anything strange happened throughout the day, I'd have to take my computer in to the shop. Can you tell me what may have happened? I am the only one who uses my computer, so there is no one here that could have changed anything, and I haven't made any changes myself to anything. Please give me some input as to why this happened. Thank you.

 

Maybe you have the screensaver set up to ask for password on resume and you can't recall your password?

 

I don't use a screensaver! I have also been getting a lot of messages saying checking connection to server, interrupting my game play on facebook and have to refresh the page many times. Lately, I've been on the internet and it suddenly closes on its own without any warnings or messages. I then have to click on my browser to get back on. I have no idea what's happening.