Strange Error Message

[DeyofAlgiers]

I was playing Civ4 this morning. I had just built the great lighthouse in one of my cities when a strange error message. You can see it in the top left corner of this image. It didnt kick me off the game or anything, as a matter of fact nothing actually happened when it popped up. I was just wondering what it ment and why it popped up. Any help would be very nice.

 

[DeyofAlgiers]

I dont know if it makes much difference... but before playing I turned off all the processes going on in the background... would this have anything to do with the error?