Ok, so access to the path is denied... but what's the path that it's trying to access???
This occurs when stepping though creating a new MDT task sequence and selecting to create new packages for the first time and unfortunately you have to re-step though all of the wizard options from scratch each time while trying to troubleshoot.
Anyway, long story short, running Process Monitor while trying to create the packages showed it failing while trying to create an autorun.inf as part of the MDT Package.
While the screen shot above shows a successfully built package, the folder we were seeing contained a temp file only.
A bit more digging narrowed it down to McAfee Anti-Virus running on the server that was blocking the creation of Autorun.inf files. Strangely enough though it didn't block the MDT installer or the creating of the deployment share.
After messing with disabling the AV and stopping services to prevent the ePO restarting the AV we ran through the MDT Task Sequence wizard again and it installed successfully.
I suppose I should have paid more attention to the note by Michael Niehaus on this old blog post for MDT 2010 Update 1