Im getting the same error. I opened the COTA estab, saved as testCOTA. Modifed some values, saved the XML, and clicked Build>Compile estab file. Im also getting the same error when I click Build>Run Estab Manager.
EDIT:
I also tried using the Establishment Manager to import/export the BTFB estab as TestBFTB estab. It created _images folder and populated it correctly but still gives me the error when I try to compile of access the Estab Manager from there.
My compiler output was: > C:\games\Command Ops 2\EMDebug.exe -compile "C:\games\Command Ops 2\Estabs\testcota.xml"