Thunderbolt display not turning on 100% of the times

Hello,

I got a 13 inch MacBook Air 1.8ghz core i7 running OS X 10.8.2 and a 27'' thunderbolt display for 1 year +.

The problem started a month ago when my computer went sleep and the thunderbolt display didn't wake up. After a few reboots on different days the display came back and I disabled the sleep option on my mac.

Now the problem is happening when I power on my mac, once in a while the display don't turn on as well.

From what I read on other topics, I've tried all the following but it didn't fixed my problem.

- Rebooting several times

- Plugging out and in the display power cord

- Disconnecting a reconnecting all cables

- Reseting the NVRAM / PRAM

- Unchecking the "Adjust Brightness Automatically"

- Deleting the file com.apple.PowerManagement.plist and rebooting

- Turning off the mac and unplugging the display for 5min + and than turning on

There are days the display turn on normally and some others I can't get it turned on. For the past two days it was working fine and today not. I know it may work tomorrow or the day after, been acting like that for 1 month!

Any other tips or ideas on how to solve my problem?

Thanks,