15" MacBook Pro Thunderbolt Display Flickering - Firmware Updates?
Since your MBP is a 2011 (and we're still in 2011), I'll assume it's still under AppleCare 1st year warranty. If so, consider getting it checked at the nearest Apple Store. Do mention you tried applying the firmware update. The list of Apple firmware and SMC updates is here.

If you don't live near an Apple Store, and if you're curious, you could try to diagnose if there's a hardware problem using Apple Hardware Test (AHT) which is a software in one of the DVD that came with your MBP. 


Insert the DVD
shut down the MBP, then 
hold down the D (for diagnostic) while you power on your MBP
Follow the on-screen menu and note down (or take a photo of the
screen) any errors reported before you call Apple Phone Support.