Q: "You shut down your computer because of a problem"

does it look like this?  http://support.apple.com/kb/TS3742.   If so, post the most recent panic: http://support.apple.com/kb/HT2546, read this also and see if it helps: http://thexlab.com/faqs/kernelpanics.html

I had this problem, which I solved. In my case, I have two user accounts, one with admin priviledges and one without. I had to login to the admin account to make the message go away.

Really simple to fix.

1. Make sure that the account you are in has Administrator privileges

2. Go into System Preferences

3. Click on Start Up Disk

4. Select the Macintosh HD OSX drive

5. Click Restart and then follow any prompts given by the computer

Once the mac restarts, your problem should be fixed.

It was the admin priviledges part of this that made the difference I think. I tried the same method with my normal user account (which is not an admin) and the problem persisted.

pheon, your solution worked for me. When logging in as an admin user, then the computer gave me details of what caused the crash, askied if I wanted to send it to Apple, and then once dealt with, the login message no longer occurred. Thanks.