Confused on the version and result

Just got the AT2 and looking to do the seasOnPass break from XP machine.  The AT2 has the AT2 software as 4.1.1 and the iOS as 4.2.1.  For some reason, the tinyumbrella won't read the AT2.  It does fine with my iPhone4 and 3GS but just read ? 411416 so I don't seem to be able to save my shsh.  It is recognized by iTunes so I know the cable has to be working.  So now when I just try to move forward with the seasOnPass, it creates an ipsw showing AppleTV2,1_4.3_8F202_SP_Restore.ipsw.  So is this for iOS 4.3 or what?  I have heard it is best to stay with 4.2.1 but I'm not sure if that means iOS 4.2.1 or AT2 software 4.2.1 so I have not proceeded ahead with the actual jailbreak yet.  I have heard it is a must to save the shsh but that does not seem to work.  Any help of explainations are truely welcomed.

The AppleTV/iOS combination can be quite confusing, but a breakdown of the AppleTV/iOS versions can be found here.

With regard to TinyUmbrella, you will need to have both the USB and power cables connected for the AppleTV to be recognized.

Unfortunately, it's too late to save your Apple 4.1.1 (iOS 4.2.1) SHSH blobs, but you can still jailbreak this version by using GreenPois0n. Should you choose to update or restore your AppleTV you will not be able to go back to this version.

Thanks for your help....I obviously miss read the tinyumbrella insturctions (rather missed the 'power up' part) and with it plugged into the wall AND the usb, it is saving the shsh.  It seems to be showing that it is saving the 4.2.1 and the 4.3.1 so why wouldn't I be able to go back?  I thought that the reason for tiny was to get the shsh before you did anything.  As best I can tell Apple stopped signing them back in early March.  Does that mean if you did not run tiny before that date it was too late (I just got my unit)?  Why is tiny now saying it is saving the AppleTV 4.2.1 (8C154)?  Also you said to use GreenPoisOn, but why not seasOnPass?  What am I missing? 

It may try to save SHSH blobs for iOS 4.2.1, but as far as I know Apple stopped 'signing' this version as soon as 4.3 was released. TinyUmbrella will only be able to save SHSH blobs for software versions that Apple is still signing.

GreenPois0n is able to jailbreak the iOS 4.2.1 software as long as it's currently installed on your AppleTV. Running Seas0nPass will upgrade your AppleTV software to the latest version during the jailbreak.

Ok, Now I understand.  And if I want XBMC to be able to read ISO files I have to go with the latest nightly which are only on the newer anyways so I guess that is the rout I'll take.  Thank you for your time and responses.