Windows 8 IGuestSession fileExists and processCreate fail

[rami]

Hi.

Host:
Windows 7 Home Premium SP1 64-bit
VirtualBox 4.2.0-r80737

Guest:
Windows 8 Enterprise 64-bit
Disabled 3D acceleration
Guest Additions installed

Calling IGuestSession_processCreate fails and IProcess_getStatus returns Error in a Windows 8 guest when I trying to programmatically launch c:\windows\system32\notepad.exe.
IGuestSession_processCreate works in Windows XP and Windows 7 guests.

I am logged into the Windows 8 machine, with my @live.com account, currently on the desktop.

I also tried IGuestSession_fileExists in a Windows 8 guest and it returns VirtualBox error: Querying file information for "c:\windows\system32\notepad.exe" failed: VERR_NOT_FOUND (0x80BB0005)

I've attached VBox.log.

Any ideas?

Thank you.

Edit:
I posted my question in the vbox-dev mailing list because it concerns the VirtualBox API
https://www.virtualbox.org/pipermail/vb ... 05329.html