Hi guys,
I don't mean to alarm anyone, but the problem may be a little deeper that we think.
Like I mentioned before, I updated 3 computers, but only one showed that error. That same computer kept showing the same error message over and over until one day, early last week, it froze during bootup.
I tryed to boot the computer via safe mode, and nothing. Got in touch with the Apple Line and we tryed all sorts of stuff to make it work, including a full HD format (we even tried to erase both the main and the Lion restore partition), without success.
I had to take the computer to an authorized repair store, and they finally got to format the hard drive, using a boot disk. After that I made a full system restore from my Time Machine and everything worked perfectly since then and the error never appeared again.
Talking to the Apple Line afterwards, they told me it could be a corrupted file that lead to both problems.
I would consider a full system backup to Time Machine and a full restore (using the Cmd+R boot), during which Lion automatically checks every copied file and rearranges them to ensure that no lingering error remains.
Like I said, this a bit in "I guess" knowledge, but I thought I'd share with you this event.
Best regards,
Sergio