整新機無法備份SHSH...

送修的iphone4回來了，但換成整新機了，IOS4.1版，立即執行tiny umbrella，但出現以下訊息，好像是4.1的SHSH已無法備份...
請教各位達人：如果無法備份IOS4.1版的SHSH，升級到IOS4.2版後，就無法降回4.1版了嗎？（目前好像沒有4.2的完美JB）..

12/31/2010 15:20:22.765 You have saved your iPhone4 4.2.1 (8C148) SHSH locally and the request was sent to CYDIA. This means that CYDIA DOES have your SHSH. Do NOT bug semaphore about the Cydia home page showing this version.
12/31/2010 15:21:06.140 This device isn't eligible for the requested build. 12/31/2010 15:21:06.140 CYDIA DOES NOT HAVE YOUR SHSH FOR iPhone4 4.0.1 (8A306) THERE IS NO WAY FOR YOU TO GET THEM. SORRY. YOU ARE JUST TOO LATE.
12/31/2010 15:21:10.250 This device isn't eligible for the requested build. 12/31/2010 15:21:10.250 CYDIA DOES NOT HAVE YOUR SHSH FOR iPhone4 4.1 (8B117) THERE IS NO WAY FOR YOU TO GET THEM. SORRY. YOU ARE JUST TOO LATE. 12/31/2010 15:22:01.750 This device isn't eligible for the requested build. 12/31/2010 15:22:01.765 CYDIA DOES NOT HAVE YOUR SHSH FOR iPhone4 4.0.2 (8A400) THERE IS NO WAY FOR YOU TO GET THEM. SORRY. YOU ARE JUST TOO LATE.
12/31/2010 15:22:09.359 This device isn't eligible for the requested build. 12/31/2010 15:22:09.375 CYDIA DOES NOT HAVE YOUR SHSH FOR iPhone4 4.0 (8A293) THERE IS NO WAY FOR YOU TO GET THEM. SORRY. YOU ARE JUST TOO LATE.
12/31/2010 15:23:02.875 This device isn't eligible for the requested build.
12/31/2010 15:23:02.890 CYDIA DOES NOT HAVE YOUR SHSH FOR iPhone4 4.2b3 (8C5115c) THERE IS NO WAY FOR YOU TO GET THEM. SORRY. YOU ARE JUST TOO LATE.
12/31/2010 15:23:02.906 Finished saving SHSHs for [Administrator 的 iPhone]
12/31/2010 15:23:02.953 Caching shsh files...
12/31/2010 15:23:02.968 Found [4] shsh files to cache...
12/31/2010 15:23:02.984 Cached [4] shsh files