Thanks for the quick response, Todd.
Just finished updating to build 22.214.171.124 & restarted system.
Error still present, though.
What are the exact steps you're taking that lead to this error?
What format and codec is the footage you're trying to replace it with?
I was working on a project off AE CS6 126.96.36.199 on a Mac.
After saving the project file and backing it up to a USB flashdrive I've brought it home to continue where I left off on my Windows laptop.
Upon opening the project file in AE the "missing footage" window appeared on screen.
Attempting to replace the missing footage caused the error.
Footage file were layers from a PSD file.
Re-save the PSD source files on your PC. This could be caused by stored references for Smart Objects or data pasted into the PSD.
Sorry for the late update, just tried your method.
I've re-saved the PSD files back to its original location. (basically saving a copy with the same file name, deleting the old one, and placing the new copy into the old file's location)
Issue still persists, though.