i need help. i have upgraded the efi firmware in my macbook pro laptop. now the screen is grey during startup. how can i rectify this problem. pls help. thanks

Hi, does it eventually log in to the Desktop?

If 10.7.0 or later...

Bootup holding CMD+r, or the Option/alt key to boot from the Restore partition & use Disk Utility from there to Repair the Disk, then Repair Permissions.

Have you done a PRAM reset, CMD+Option+p+r...

http://support.apple.com/kb/HT1379

In fact, do 3 in a row, takes a bit of time.

Intel-based Macs: Resetting the System Management Controller (SMC)...

http://support.apple.com/kb/HT3964