The problem was solved as follows:
- Exit Delphi XE6.
- Rename your current <project>.dproj file to <project>.dproj.error.
- Create a new dummy project with a simple empty form in a different directory and save it.
- Edit dummy.dproj in Notepad and replace all occurrences of "dummy" with your <project> name.
- Save the file as <project>.dproj in the original project directory.
- Restart Delphi XE6 and try to build your project again.
