changing 'Directories/Conditionals' Options causing problems

I have created a project with default Options settings, which
when built, merely dumped all of the files into the current
directory with the source and the .bpr project file.

I then wished to separate the files into the \bin \obj \src \inc
directories. Having done so, and edited the Options to reflect
these paths, I saved all and re-built the project, which was
fine.

I then tried to re-build the project shortly afterwards. This
time I get the error message:

    "error in module mainform : declaration of class is missing
     or incorrect"

I have changed no code at all, and the IDE will not let me
compile any files within the project, or build the project
itself. I have tried:

1. moving the .bpr and accompanying files around the directories
   and adjusting the paths to fit, in order that I could see any
   dependencies between any files, and perhaps spot why moving
   the source and headers etc could cause this problem.
2. Deleting the .tds file so that a fresh one is generated on
   the first build.
3. Looking through the project file XML file to see if there was
   anything that looked out of place, like paths which have not
   been updated etc. - No luck.
3. Changing it all back to the way it was, which solves the
   problem, but is messy having all of the files in one dir...!!

I can only think that there is something in the project that is
reset back to the way it was originally set up at some point, but
alas I cannot see what.

I hope I have explained this well enough, but I suspect not!

If anyone thinks they may be able to help, I would welcome an email or a response here.

Many thanks...James