Sounds like time for a PRAM reset. Here's how:
1. Power down the machine.
2. Locate the following keys on your keyboard in preparation for Step 4:
‘command’ – ‘option’ – ‘P’ – ‘R’
3. Press the ‘power on’ button.
4. Immediately – and before the grey screen appears – hold down ‘command-option-P-R’ all together.
5. Keep them held down until you’ve heard the start-up chime twice. After you release them you should hear it again, and hopefully your Mac will boot up as normal.
In which case, start up holding down the 'shift' key while you power on to enable Safe Mode. Keep the shift key held down till you see the apple logo and the progress bar (then you can release it). When the progress bar finishes log in (Safe Mode will take a long time to log in because its doing some system clean up routines among other things).
When you finally get logged in, go to
> System Preferences...Users & Groups | Login Items
What's in the list? Chances are there's something in there that is causing your system to slow boot. You can simpy remove everything from that list (highlight all items, and click the minus '-' key directly below them), or post the names of the apps that are there for feedback on likely troublemakers.
After removing items from the list, restart your mac normally and see if the boot up time has improved.
You can get this if you have shutdown the computer using the power button or if it thinks there is some sort of a problem. It will run a scan which can take some time. Have you let it go through this stage and logged in to your account? If it still does the same, try booting into the recovery partition (Hold Opt during power on and select the RP) and running Repair Disk and Permissions from the disk utility. If necessary, you can also download a fresh copy of the OS and install it from there.
It seems that many people have same issues (me too). After upgrading in 10.8.3 many MacBooks pro needing more than 5 minutes to boot. It has something to do with the internal sd drive. By some people the problem is fixed when they remove the sd card from card-reader by other by placing a sd card in reader. Apple must solve this problem!!!!