I have one machine running Windows 7 and a reserve running Windows 8; the former has MC 6.5 and the latter MC 6 installed (I could not successfully install 6.5 to the Windows 8 machine). I am not using any specialised hardware.
The Windows 7 machine will produce a lengthy Quicktime export without difficulty but the other hangs (for example after 54'59" of 13h01'00" estimated) with the message "Making fast start movie".
Avid 6 works well on Windows 8 in other respects so I wonder whether it's really implicated here or whether something else is at work (such as the way I've copied Avid MediaFiles etc. from drive to drive).
I appreciate that Avid is not yet certified for Windows 8 but wondered whether anyone had any thoughts about what kind of issue triggers this glitch.
As Job says, the lack of qualification maybe the issue, but 6.0 did have an known bug which caused it to hang on 'making fast start movie' whether or not you deactivated that option in the export settings. This was resolved with the release of 6.0.3.