I'm being quite serious.
Animator is trying to collect files for an AE project to take home on a drive to work over the weekend. It keeps failing, claiming a file cannot be found. This is CC 2014 (AE 13.2).
The file is definitely where it should be in the original project, and it seems it's even being copied over to external drive, just not properly linked up. Multiple tries fail on different files. Uh, what? Everything is exactly where it is and should be.
So, I wouldn't believe this myself if I didn't see it myself. Don't touch any input devices, or better yet just unplug them entirely. My coworker found the following links at Adobe and Creative Cow, and sure enough unplugging the Wacom and sitting on our hands did the trick (sitting on hands may not be necessary but I wouldn't risk it).
Definitely a bug of some sort, or possibly evidence that After Effects is becoming sentient, deciding it no longer likes to be touched by our clumsy human appendages.