This is the fix i found through talking with intrepid support and some devs.
this is only for the non-pak file error 5.
you must relocate steam out of the program X86 folder. goto steam and save the steam app folder to desktop.
(cut paste if not enough space to copy)
uninstall steam, reinstall on C: drive in new folder. paste Steam app folder back into steam log back into steam. launch game.. that fixed it for me.
