Why  does my MacBook Pro's keyboard freeze when it wakes up so I have to hard reboot? Sometimes, but not every time, when I open my MacBook Pro to wake it from sleep, the keyboard doesn't respond, so I have to reboot my Mac using the power button.

There's a good chance that it happens when I close the lid without the laptop being plugged into power (the MagSafe plug), then plug in either power or headphones before I wake the computer again.

It is a MacBook Pro 15"(2011), 2.2Ghz Intel Core i7, 500GB 5400 RPM, 8G RAM running
Mac OS X Lion 10.7.3 (11D50d). I have zh-CN (PRC Chinese) (Mainland China, simplified characters) as the preferred language for all users by default. I upgraded my Lion one by one (from 10.7 to 10.7.1,... till 10.7.3) and while upgrading, I didn't get any error or alert. So the updates went well.

I tried to solve it following a work around involving inserting and unplugging my headphones, but that didn't work out.

Is there any solid solution, or is this a known MacBook Pro issue?
I'd suggest taking the laptop into your local Apple Store or an Apple Authorized repair location. This definitely seems like a hardware fault: I would hope they'd replace or repair the laptop. Make sure you make a complete backup before you go to the store.