Okay so I have this problem. I turn on my Macbook (the old, white one). Its pretty new, I got it in July. Now when I turn it on the gray screen comes up. Afterwards, the blue screen comes up and stays there for a really long time, maybe upwards of 5 minutes. Then it goes back to the gray screen for a few moments, then the blue screen, but this time I can see the mouse. THEN I get to the desktop and everything else is fine. What's the problem?

Under Applications/Utilited open Disk utility and click the First Aid tab. Then repair permissions. This should speed your boot.
You can check the drive under First-aid also but to repair directory errors you will need another utility that will boot from a CD or fire wire. There are some utilities that will repair most of the directory from a HD boot I have not tried them My employer specifies the use of Disk Warrior then if that fails a reinstall from a disk image. Be it good or bad those are the rules I have to play by so my exposure to other disk repair utilities is limited. Try the repair permissions it should help