I'm not seeing that here. Export through AME works just fine even with AE closed, as I'd expect.
Not sure what to tell you Jim.
1) Update all products to CC version.
2) Open PR CS6 project in PR CC which then "converts and saves" to CC version.
3) Right click on any clip and "replace with AE composition"
4) Edit in AE CC and save.
5) Save PR CC project.
6) Close PR & AE.
7) Launch AME CC and open PR CC project/sequence.
8) Render outputs with "media offline" plates in all instances.
Repeat above steps with the omission of Step 6, AME CC renders correctly.
I can do this multiple times with the exact same result.
***Win 7 Pro 64bit
It turns out that any dynamically linked CC apps must be run by the same user on the same machine in order to work properly. In this case, PR and AME were being run as a standard user on the workstation while AE was being run as administrator via the shortcut launch properties. The latter being necessary to have certain plugins function properly in AE CC. Modifying the AE shortcut to not run as administrator resolves dynamic linking issues.
Although it can be argued that logically all Adobe apps should be run by the "same user" on the workstation, it would be nice for the dynamic link engine to be more "real world" about linking projects on the same workstation in the case where a particular resource needs to be launched as an administrator. Security considerations in towe, this ain't top secret government or banking data risk management folks. Lighten up. Maybe a little warning box that pops up and says "such and such needs to be run as administrator....do you allow?".....after all this is EXACTLY what the OS does anyway when you launch as anyone other than the administrator from a shortcut. Quite reasonable for you (Adobe) to simply cascade the behavior.