@Ashley, in C2 r106 the problem still going.
I have tested manually to convert .ogg from D:\Program Files\Construct 2\tools\audio\oggenc2.exe
From command prompt says:
"This version of D:\Program Files\Construct 2\tools\audio\oggenc2.exe is not compatible with the version of Windows you're running. Check your computer's system information and then contact the software publisher."
This is screenshot:
I'm using Windows 8 RTM (Enterprise Evaluation
I have try it to in C2 r103.2 Stable Version, the ogg tools works fine.