Problema resolvido. Acontece que o meu provedor decide definir o modem a cabo sem o modo de ligação sem me avisar. Quando o problema do modem é resolvido com o ISP, o problema não aparece novamente.
Eu vejo o erro 0x80072ee2 e o seguinte do windowsupdate.log
2014-09-27 02:26:45:866 480 69c AU Triggering AU detection through DetectNow API
2014-09-27 02:26:45:866 480 69c AU Additional Service {117CAB2D-82B1-4B5A-A08C-4D62DBEE7782} with Approval type {Scheduled} added to AU services list
2014-09-27 02:26:45:866 480 69c AU Triggering Online detection (interactive)
2014-09-27 02:26:45:867 480 c30 AU #############
2014-09-27 02:26:45:867 480 c30 AU ## START ## AU: Search for updates
2014-09-27 02:26:45:867 480 c30 AU #########
2014-09-27 02:26:45:867 480 c30 AU Additional Service {117CAB2D-82B1-4B5A-A08C-4D62DBEE7782} with Approval type {Scheduled} added to AU services list
2014-09-27 02:26:45:868 480 c30 IdleTmr WU operation (CSearchCall::Init ID 2) started; operation # 16; does use network; is not at background priority
2014-09-27 02:26:45:868 480 c30 IdleTmr Incremented PDC RefCount for Network to 1
2014-09-27 02:26:45:868 480 c30 IdleTmr Incremented idle timer priority operation counter to 1
2014-09-27 02:26:45:868 480 c30 Agent *** START *** Queueing Finding updates [CallerId = AutomaticUpdatesWuApp Id = 2]
2014-09-27 02:26:45:868 480 c30 AU <<## SUBMITTED ## AU: Search for updates [CallId = {115760E7-ECF1-4F4A-867F-B4736469BB20} ServiceId = {9482F4B4-E343-43B6-B170-9A65BC822C77}]
2014-09-27 02:26:45:868 480 76c Agent *** END *** Queueing Finding updates [CallerId = AutomaticUpdatesWuApp Id = 2]
2014-09-27 02:26:45:868 480 76c Agent *************
2014-09-27 02:26:45:868 480 76c Agent ** START ** Agent: Finding updates [CallerId = AutomaticUpdatesWuApp Id = 2]
2014-09-27 02:26:45:868 480 76c Agent *********
2014-09-27 02:26:45:868 480 76c Agent * Online = Yes; Ignore download priority = No
2014-09-27 02:26:45:868 480 76c Agent * Criteria = "IsInstalled=0 and DeploymentAction='Installation' or IsPresent=1 and DeploymentAction='Uninstallation' or IsInstalled=1 and DeploymentAction='Installation' and RebootRequired=1 or IsInstalled=0 and DeploymentAction='Uninstallation' and RebootRequired=1"
2014-09-27 02:26:45:868 480 76c Agent * ServiceID = {9482F4B4-E343-43B6-B170-9A65BC822C77} Windows Update
2014-09-27 02:26:45:868 480 76c Agent * Search Scope = {Machine & All Users}
2014-09-27 02:26:45:868 480 76c Agent * Caller SID for Applicability: S-1-5-21-2731448095-1286900904-3549611129-1001
2014-09-27 02:26:45:869 480 76c SLS Retrieving SLS response from server...
2014-09-27 02:26:45:869 480 76c SLS Making request with URL HTTPS://sls.update.microsoft.com/SLS/{9482F4B4-E343-43B6-B170-9A65BC822C77}/x64/6.3.9600.0/0?CH=941&L=en-US&P=&PT=0x30&WUA=7.9.9600.17031
2014-09-27 02:26:46:399 480 76c Misc Validating signature for C:\Windows\SoftwareDistribution\SLS82F4B4-E343-43B6-B170-9A65BC822C77\sls.cab with dwProvFlags 0x00000080:
2014-09-27 02:26:46:402 480 76c Misc Microsoft signed: NA
2014-09-27 02:26:46:402 480 76c Misc Infrastructure signed: Yes
2014-09-27 02:26:46:404 480 76c Misc Validating signature for C:\Windows\SoftwareDistribution\SLS82F4B4-E343-43B6-B170-9A65BC822C77\TMPA473.tmp with dwProvFlags 0x00000080:
2014-09-27 02:26:46:407 480 76c Misc Microsoft signed: NA
2014-09-27 02:26:46:407 480 76c Misc Infrastructure signed: Yes
2014-09-27 02:26:46:408 480 76c EP Got 9482F4B4-E343-43B6-B170-9A65BC822C77 redir Client/Server URL: "https://fe2.update.microsoft.com/v6/ClientWebService/client.asmx"
2014-09-27 02:26:46:410 480 76c Setup Checking for agent SelfUpdate
2014-09-27 02:26:46:410 480 76c Setup Client version: Core: 7.9.9600.17031 Aux: 7.9.9600.17031
2014-09-27 02:26:46:411 480 76c EP Got 9482F4B4-E343-43B6-B170-9A65BC822C77 redir SelfUpdate URL: "https://fe2.update.microsoft.com/v10/3/windowsupdate/selfupdate"
2014-09-27 02:27:07:411 480 76c Misc WARNING: Send failed with hr = 80072ee2.
2014-09-27 02:27:07:411 480 76c Misc WARNING: Proxy List used: <(null)> Bypass List used : <(null)> Auth Schemes used : <None>
2014-09-27 02:27:07:411 480 76c Misc WARNING: Send request failed, hr:0x80072ee2
2014-09-27 02:27:07:411 480 76c Misc WARNING: WinHttp: SendRequestUsingProxy failed for <https://fe2.update.microsoft.com/v10/3/windowsupdate/selfupdate/wuident.cab>. error 0x80072ee2
2014-09-27 02:27:07:411 480 76c Misc WARNING: WinHttp: SendRequestToServerForFileInformation MakeRequest failed. error 0x80072ee2
2014-09-27 02:27:07:411 480 76c Misc WARNING: WinHttp: SendRequestToServerForFileInformation failed with 0x80072ee2
2014-09-27 02:27:07:411 480 76c Misc WARNING: WinHttp: ShouldFileBeDownloaded failed with 0x80072ee2
Minha grande pergunta é: o que é o link ? Executá-lo no navegador chrome não leva a lugar nenhum (não recupera o arquivo), e posso acessar todos os outros sites da internet. É uma área de trabalho para casa, portanto, nenhum firewall corporativo e tal. Eu desabilito o firewall e não faz diferença.
Problema resolvido. Acontece que o meu provedor decide definir o modem a cabo sem o modo de ligação sem me avisar. Quando o problema do modem é resolvido com o ISP, o problema não aparece novamente.