Well, this looks like an issue from several years ago. Occurs in a clean Windows 8.1 installation. No viruses, nothing out of the ordinary. Same configuration, software and documents been working in W8 without issues. AV Windows Defender included with W8.1, browser IE + Firefox, though I almost don't use the last one.
Offending process command line: "C:\Windows\sysWow64\SearchProtocolHost.exe" Global\UsGthrFltPipeMssGthrPipe_S-1-5-21-856921921-1256859959-3533039330-10011_ Global\UsGthrCtrlFltPipeMssGthrPipe_S-1-5-21-856921921-1256859959-3533039330-10011 1 -2147483646 "Software\Microsoft\Windows Search" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT; MS Search 4.0 Robot)" "C:\ProgramData\Microsoft\Search\Data\Temp\usgthrsvc" "DownLevelDaemon" "1"
Tried rebuilding indexes and also leave it running for a while with no luck. Process fires itself no matter I'm actually using the computer. It's pretty annoying and I have to stop Windows Search service each time this gets stuck.