I have been trying to save SHSH since the beginning with TinyUmbrella but without any luck. For some reason TU thinks that the AppleTV is in recovery mode but it's not. I used to have the same problem since the beginning when I bought it back in April 2011. I had updated to the latest version without any luck. Now I am running 4.3 (8F455) and today I even managed to jailbreak it for first time successfully using Seas0nPass. Everything seems to run fine with my AT2, even the jailbreak was smooth without any problems.
The issue is the following:
When I plug Apple TV, TU detects it as a Recovery Device with a false ECID which updates every time that I disconnect and reconnect ATV2 through USB. If I click Exit Recovery, it will re-detect it with the same false ECID, which is strange because if I unplug and replug I get a different one. I tried to do Fix Recovery directly from TU and I even tried the dos application from TU to Fix recovery but it didn't change anything. My ATV2 is NOT in recovery mode, even though TU thinks it is. When I am in DFU mode, TU does not detect anything. If I keep unplugging and replugging while TU is open, I get every time a different ECID the decimal is 10 digits such as 1425613463. At the bottom TU says the Device is not connected.
I have been trying the latest Tinyumbrella v5.00.12 but the earlier versions when I was trying it in the past had the same problem.
I had the same problem with tiny umbrella and the way I got it to recognize the device not being in recovery mode was to have it plugged in with both the power cable and the usb cable
it then found the device and was able to save the SHSH