Hmmm.... @yiming: I'm sorry to say that, but I have absolutely no clue about what is happening on your device. CM seems to be working ok for everyone else, and there is no sign of an exception being thrown or anything, so I can't tell what could be causing the issues you're describing.
Sadly, my only other suggestion would be to clear the collections DB entirely, either by manually removing /var/local/cc.db, or by performing a factory reset, and to see if the problem goes away. The database might be corrupted or inconsistent, and I dimly remember that this solved some funky problems someone else was having.
The memory warnings are normal, AFAIK they get logged on every device, but don't cause any harm. They just state the facts - namely that the Kindle doesn't have much RAM.
And, @nasser, to make it totally clear (NiLuJe already explained it quite well): think of CM as simply being a database editor for the collections database. How that database is actually used by the Kindle framework is totally out of control, and out of scope, of CM.
I personally don't use the cover view mode (I prefer the list mode), and I don't remember experiencing any glitches when navigating around in collections on the home screen.