Here's the error sequence after a reboot...
Code:
StageFile (2): flags: 8 app: (null) comp: Microsoft-Windows-WindowsUpdateClient-ActiveX, Version = 7.6.7600.320, pA = PROCESSOR_ARCHITECTURE_IA32_ON_WIN64 (10), Culture neutral, VersionScope = 1 nonSxS, PublicKeyToken = {l:8 b:31bf3856ad364e35}, Type neutral, TypeName neutral, PublicKey neutral file: [ml:22{11},l:20{10}]"wuwebv.dll" srcfile: @0x20f198
2015-05-07 22:00:08, Error CSI 00000799 (F) A previous transaction requested a reboot, so you cannot commit any transactions until you reboot.
[gle=0x80004005]
2015-05-07 22:00:08, Error CSI 0000079a (F) STATUS_REQUEST_OUT_OF_SEQUENCE #19032367# from Windows::COM::CComponentStore::ApplyTransactionNow(...)[gle=0xd000042a]
2015-05-07 22:00:08, Error CSI 0000079b@2015/5/7:14:00:08.526 (F) d:\win7sp1_gdr\base\wcp\componentstore\com\store_transaction.cpp(1841): Error STATUS_REQUEST_OUT_OF_SEQUENCE originated in function Windows::COM::CComponentStore::ApplyTransactionNow expression: (null)
[gle=0x80004005]
2015-05-07 22:00:18, Error CSI 0000079c (F) HRESULT_FROM_WIN32(ERROR_REQUEST_OUT_OF_SEQUENCE) #19032228# from Windows::COM::CPendingTransaction::IStorePendingTransaction_Apply(...)[gle=0x80070308]
2015-05-07 22:00:18, Error CSI 0000079d (F) HRESULT_FROM_WIN32(ERROR_REQUEST_OUT_OF_SEQUENCE) #19030795# from Windows::ServicingAPI::CCSITransaction::ICSITransaction2_AddFiles(Flags = 1, a = @0x425320, fn = @0x425b20, fp = @0x426320, disp = 0, op = 0)[gle=0x80070308]
2015-05-07 22:00:18, Info CBS Failed to add to transaction package: WUClient-SelfUpdate-ActiveX~31bf3856ad364e35~amd64~~7.6.7600.320 [HRESULT = 0x80070308 - ERROR_REQUEST_OUT_OF_SEQUENCE]
2015-05-07 22:00:18, Error CBS Failed to stage execution package: WUClient-SelfUpdate-ActiveX~31bf3856ad364e35~amd64~~7.6.7600.320 [HRESULT = 0x80070308 - ERROR_REQUEST_OUT_OF_SEQUENCE]
2015-05-07 22:00:18, Info CSI 0000079e@2015/5/7:14:00:18.803 CSI Transaction @0x32baee0 destroyed
Try this...
Open an Elevated Command Prompt, and run the following commands...
REG LOAD HKLM\COMPONENTS C:\Windows\System32\config\COMPONENTS
REG DELETE HKLM\COMPONENTS /V PendingRequired
reboot and then attempt Windows Update again.