I had the exact same issue now. Without any particular reason for it to start, or in other words, I did not make any changes to the project file. Your advice set me on the right path. But in Notepad it did NOT show any offending characters, so I copied that problem line of code, then pasted it into another Notepad. Doing so removed the illegal char, then copied the new line and replaced the old line. The offending char was now gone and Delphi compiled again.