As noticed by iH8Sn0w we can confirm that Apple has released a new firmware for the (GSM) iPhone 4. This firmware is iOS 5.1.1 Build 9B208 and at this time has not been documented.
With a new firmware being released by Apple this is a good indication that you should save your SHSH blobs for iOS 5.1.1 if you have not already. This will allow you to downgrade your iOS device if you accidentally update to a firmware that has not been Jailbroken yet. TinyUmbrella has been updated to version 5.11.01 to support this new build, head here to download it.
The good news is Absinthe 2.0.2 has been released to untethered jailbreak iPhone 4 on iOS 5.1.1 Build 9B208 and with bug fixed. If you failed jailbreaking with Absinthe 2.0, try the new update. Click here to download. And if you need a tutorial, head to here.