MacBook Pro: Power button disabled for three seconds after connecting power adapter
Summary
You may notice that your MacBook Pro, MacBook Pro (17-inch), MacBook Pro (15-inch Glossy), MacBook Pro (15-inch Core 2 Duo) or MacBook Pro (17-inch Core 2 Duo) computer's power button is disabled for up to three seconds after you connect the MagSafe power adapter to the computer.
Products Affected
MacBook Pro
This is normal behavior—your MacBook Pro and MagSafe adapter are functioning correctly. When you first connect the power adapter to the MacBook Pro, your computer's System Management Controller (SMC) shuts off power to the power button while the system communicates with the adapter.