Jailbreak Broken...
I am in exactly the same boat. iTunes is playing, a call trys to come through, the signal drops, (happens like this every couple days) and usually the bars come back after a few seconds of "no service" and "searching". Today the bars didn't come back and when I tried to hard reset, the phone wouldn't boot. I had to reinstall, I've followed all the instructions I can find, but still can't get iTunes to accept the old 3.1.2. I have SHSH on file with cydia, (it said on file for 3.1.3 in cydia). I had an untethered jailbreak with blackra1n.
Here's the error I get when I try to downgrade:
2010-03-24 09:20:58.811 iTunes.exe[9536:167c]: restore library built Aug 24 2009 11:22:55
2010-03-24 09:20:58.811 iTunes.exe[9536:167c]: iTunes: iTunes 9.0.3.15
2010-03-24 09:20:58.811 iTunes.exe[9536:167c]: iTunes: Software payload version: 7D11 (option key)
2010-03-24 09:20:58.975 iTunes.exe[9536:1d4c]: iTunes: Specifying UOI boot image
2010-03-24 09:20:58.976 iTunes.exe[9536:1d4c]: AMRAuthInstallAttemptSimple(HTTP)Request: attempting to connect to gs(dot)apple(dot)com:80/
2010-03-24 09:20:59.081 iTunes.exe[9536:1d4c]: _AMRAuthInstallIsHttpServerResponsive: server reponse status code: 200. status text: OK
2010-03-24 09:20:59.110 iTunes.exe[9536:2570]: <DFU Device 06F90F88>: operation 44 progress -1
2010-03-24 09:20:59.112 iTunes.exe[9536:2570]: phoning home to gs.apple.com:80
2010-03-24 09:20:59.112 iTunes.exe[9536:2570]: tss_add_entry: ApECID
2010-03-24 09:20:59.112 iTunes.exe[9536:2570]: tss_add_entry: ApChipID
2010-03-24 09:20:59.112 iTunes.exe[9536:2570]: tss_add_entry: ApBoardID
2010-03-24 09:20:59.112 iTunes.exe[9536:2570]: tss_add_entry: ApProductionMode
2010-03-24 09:20:59.113 iTunes.exe[9536:2570]: tss_add_entry: ApSecurityDomain
2010-03-24 09:20:59.113 iTunes.exe[9536:2570]: tss_add_entry: UniqueBuildID
2010-03-24 09:20:59.113 iTunes.exe[9536:2570]: tss_add_entry: @Locality
2010-03-24 09:20:59.113 iTunes.exe[9536:2570]: tss_add_entry: iBSS
2010-03-24 09:20:59.113 iTunes.exe[9536:2570]: tss_add_entry: iBEC
2010-03-24 09:21:01.268 iTunes.exe[9536:2570]: [tss] error from server=94 (This device isn't eligible for the requested build.)
2010-03-24 09:21:01.268 iTunes.exe[9536:2570]: server error (94): This device isn't eligible for the requested build.
2010-03-24 09:21:32.169 iTunes.exe[9536:167c]: iTunes: Restore error 3194
Did saurik change the IP of his signature server? I have:
74.208.10.249 gs.apple.com
in my "hosts" file.
I'm mildly frustrated at this point.
PS: I had to change the URL above because I'm a new user.