Strange Component Happenings

I have modified the TCombobox component to have a ReadOnly property and give it some additional functionality. The new component is installed and I am able to drop the comp onto forms and manipulate it's ReadOnly property at design time.

I have created a dialogue form which uses this component, and has previously compiled and work perfectly. I tried to recompile the dialogue today and got many errors.

On each line where I reference TNewCombo.ReadOnly I get the message Undeclared Identifier. I can still manipluate this property at design time.

If I open a new project and place the new component on a form, I can then reference it's ReadOnly prop at runtime and design time.

I have tried:

recompiling the component package
build all
replacing the components with new comps

None of the above offers any success. Any suggestions ?