Is that problem reproducable with a new blank application or only specific to a certain project?
Make sure the date/time settings of your computer are correct, they might confuse the compiler. Also if you are editing the correct files (might be duplicates of what the project uses). Check for possible dcus somewhere that might be taken.
As a side note: you don't need to delete the
dcu files. Hit Shift+F9 which does a build instead of a compile.