Howling:11 doesn't know River?

This might have been addressed or I'm missing something really big(sorry if I am, please don't be angry :-/) but how does 11 not know River very well? In the Silence in the library 2-parter, River knew who 10 was and we found out that in her timeline, he had taken her places and ended up crying because he knew he would die in the library. Now, 11 says he doesn't know her very well. I don't understand this; is it because she knows his faces, but not their order so it was 11 who cried after he got to know her?

Similarly, the sonic screwdriver she has previously belonged to 10. So did 11 go back, get his old screwdriver, and then give it to River? Sorry if this doesn't make sense, I'm just a little baffled by the issue. :P Thanks for any help!
 * It may also be 12 or 13 who cried. We have no idea how long the relationship/story arc will last. Additionally, the Doctor could have simply obtained a SS similar to 10's SS. -- Bold  Clone  23:01, December 29, 2010 (UTC)