Hi,
Please check if there's a bug text at the following location, and post it's contents please if present.
C:\
Bug.txt
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Delete the present copy of combofix from your desktop and download a fresh copy. You can download it on a removable medium and transfer it to your desktop if you're still unable to access the internet.
Please make sure that your security tools and your antivirus is disabled prior to running of Combofix. Please refer to
this page if you're unsure about how to disable them.
Click the Windows 'Start' button > Select 'Run' - then copy/paste the following text in bold (exactly as it is below) into the run box & click OK. (be sure to include the quote marks)
"%userprofile%\desktop\combofix.exe" /killall
Post the C:\ComboFix.txt it produces