Which version of ID, including the build number. You can find that on Windows by holding the Ctrl key while you press About InDesign in the help menu, or on Mac by pressing the Cmd key while choosing the same command in the InDesign menu.
What happens when you try to open the exported IDML?
Either the IDML is damaged, or it isn't really an IDML file. How did you make it?
126.96.36.1993 is the latest build, I believe (333 is the build number).
See what sort of error messages you can find in Event viewer.
I created it by exporting as IDML (using the export... function). It comes up with these error messages (the top one first, then the bottom - I just put them together in an image) when I do it but creates a file anyway
Is this the relevant info from the Event viewer?
Faulting application name: InDesign.exe, version: 188.8.131.523, time stamp: 0x4f6b9e72
Faulting module name: Public.dll, version: 184.108.40.2063, time stamp: 0x4f6b9c77
Exception code: 0xc0000005
Fault offset: 0x002451ee
Faulting process ID: 0x1ba0
Faulting application start time: 0x01d04c5473756b5f
Faulting application path: C:\Program Files (x86)\Adobe\Adobe InDesign CS5.5\InDesign.exe
Faulting module path: C:\Program Files (x86)\Adobe\Adobe InDesign CS5.5\Public.dll
Report ID: da18f802-b847-11e4-be96-c81f662f6554
Faulting package full name:
Faulting package-relative application ID:
Yeah, that's relevant, but unfortunately not terribly helpful from Event viewer.
You said initially you trashed the prefs. Did you use one of the methods here: Replace Your Preferences or just get only one of the files? Failure to do a complete replacement doesn't always work.
you might also want to see Troubleshoot font problems | Windows
Was the application installed after Win8, or was this an OS upgrade?