Problems w/ explorer.exe

Hello, experts.. I've been having trouble w/ explorer.exe when I turn on my computer or restart it.
I get the following message:
Explorer.exe - Error
Instruction 0x784abd4e references to memory 0x006c0075. Memory cannot be written. Click OK to end program.

I've run everything I know (CWshredder, Adaware, Spybot) and I got my new log here:

Logfile of HijackThis v1.96.4
Scan saved at 11:22:34, on 9/4/2004
Platform: Windows 2000 SP4 (WinNT 5.00.2195)
MSIE: Internet Explorer v5.00 SP4 (5.00.2920.0000)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\system32\spoolsv.exe
C:\ARQUIV~1\Grisoft\AVG6\avgserv.exe
C:\WINDOWS\System32\svchost.exe
C:\ARQUIV~1\Iomega\System32\AppServices.exe
C:\WINDOWS\system32\MSTask.exe
C:\WINDOWS\System32\WBEM\WinMgmt.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\ZipToA.exe
C:\Arquivos de programas\Iomega\AutoDisk\ADService.exe
C:\WINDOWS\system32\Fmctrl.EXE
C:\Arquivos de programas\Adaptec\Easy CD Creator 5\DirectCD\DirectCD.exe
C:\Arquivos de programas\Iomega\AutoDisk\ADUserMon.exe
C:\Arquivos de programas\Iomega\DriveIcons\ImgIcon.exe
C:\Arquivos de programas\QuickTime\qttask.exe
C:\Arquivos de programas\Discador Telefonica\ddt.exe
C:\WINDOWS\system32\internat.exe
C:\Arquivos de programas\MSN Messenger\MsnMsgr.Exe
C:\REGINA\WINZIP7.0\WZQKPICK.EXE
C:\Arquivos de programas\Adobe\Acrobat 4.0\Distillr\AcroTray.exe
C:\WINDOWS\explorer.exe
C:\Arquivos de programas\Internet Explorer\iexplore.exe
C:\REGINA\WINZIP7.0\winzip32.exe
C:\Documents and Settings\Administrador\Configurações locais\Temp\HijackThis.exe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Bar = http://www.ubbi.com.br/busca/ieak/search.html
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Local Page = c:\windows\SYSTEM\blank.htm
O2 - BHO: (no name) - {53707962-6F74-2D53-2644-206D7942484F} - C:\ANTIVI~1\SPYBOT~1\SDHelper.dll
O3 - Toolbar: &Rádio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\System32\msdxm.ocx
O4 - HKLM\..\Run: [SystemTray] SysTray.Exe
O4 - HKLM\..\Run: [FmctrlTray] Fmctrl.EXE
O4 - HKLM\..\Run: [NvCplDaemon] RUNDLL32.EXE NvQTwk,NvCplDaemon initialize
O4 - HKLM\..\Run: [AdaptecDirectCD] "C:\Arquivos de programas\Adaptec\Easy CD Creator 5\DirectCD\DirectCD.exe"
O4 - HKLM\..\Run: [ADUserMon] C:\Arquivos de programas\Iomega\AutoDisk\ADUserMon.exe
O4 - HKLM\..\Run: [Iomega Startup Options] C:\Arquivos de programas\Iomega\Common\ImgStart.exe
O4 - HKLM\..\Run: [Iomega Drive Icons] C:\Arquivos de programas\Iomega\DriveIcons\ImgIcon.exe
O4 - HKLM\..\Run: [Deskup] C:\Arquivos de programas\Iomega\DriveIcons\deskup.exe
O4 - HKLM\..\Run: [QuickTime Task] "C:\Arquivos de programas\QuickTime\qttask.exe" -atboottime
O4 - HKLM\..\Run: [ddt] "C:\Arquivos de programas\Discador Telefonica\ddt.exe" -F
O4 - HKLM\..\Run: [LoadQM] loadqm.exe
O4 - HKCU\..\Run: [internat.exe] internat.exe
O4 - HKCU\..\Run: [MsnMsgr] "C:\Arquivos de programas\MSN Messenger\MsnMsgr.Exe" /background
O4 - Global Startup: Microsoft Office.lnk = C:\Arquivos de programas\Microsoft Office\Office\OSA9.EXE
O4 - Global Startup: WinZip Quick Pick.lnk = C:\REGINA\WINZIP7.0\WZQKPICK.EXE
O4 - Global Startup: Adobe Gamma Loader.exe.lnk = C:\Arquivos de programas\Arquivos comuns\Adobe\Calibration\Adobe Gamma Loader.exe
O4 - Global Startup: Acrobat Assistant.lnk = C:\Arquivos de programas\Adobe\Acrobat 4.0\Distillr\AcroTray.exe
O4 - Global User StartupMicrosoft Office.lnk = C:\Arquivos de programas\Microsoft Office\Office\OSA9.EXE
O4 - Global User StartupWinZip Quick Pick.lnk = C:\REGINA\WINZIP7.0\WZQKPICK.EXE
O4 - Global User StartupAdobe Gamma Loader.exe.lnk = C:\Arquivos de programas\Arquivos comuns\Adobe\Calibration\Adobe Gamma Loader.exe
O4 - Global User StartupAcrobat Assistant.lnk = C:\Arquivos de programas\Adobe\Acrobat 4.0\Distillr\AcroTray.exe
O6 - HKCU\Software\Policies\Microsoft\Internet Explorer\Control Panel present
O9 - Extra 'Tools' menuitem: Sun Java Console (HKLM)
O14 - IERESET.INF: SEARCH_PAGE_URL=&http://home.microsoft.com/intl/br/access/allinone.asp
O14 - IERESET.INF: START_PAGE_URL=http://www.msn.com.br
O14 - IERESET.INF: MS_START_PAGE_URL=http://www.msn.com.br
O16 - DPF: {02BF25D5-8C17-4B23-BC80-D3488ABDDC6B} (QuickTime Object) - http://www.apple.com/qtactivex/qtplugin.cab
O16 - DPF: {166B1BCA-3F9C-11CF-8075-444553540000} (Shockwave ActiveX Control) - http://download.macromedia.com/pub/shockwave/cabs/director/sw.cab
O16 - DPF: {2BC66F54-93A8-11D3-BEB6-00105AA9B6AE} (Symantec AntiVirus scanner) - http://security.symantec.com/SSC/SharedContent/vc/bin/AvSniff.cab
O16 - DPF: {74D05D43-3236-11D4-BDCD-00C04F9A3B61} (HouseCall Control) - http://a840.g.akamai.net/7/840/537/0fb5e03023def1/housecall.antivirus.com/housecall/xscan53.cab
O16 - DPF: {C2FCEF52-ACE9-11D3-BEBD-00105AA9B6AE} (Symantec RuFSI Registry Information Class) - http://security.symantec.com/SSC/SharedContent/common/bin/cabsa.cab
O16 - DPF: {D27CDB6E-AE6D-11CF-96B8-444553540000} (Shockwave Flash Object) - http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab
O17 - HKLM\System\CCS\Services\Tcpip\..\{F58D897C-33DB-4DB8-8C20-4079960139A8}: NameServer = 200.204.0.138 200.204.0.10

Any idea of what might be going on???