When you get internal errors it has rarely to do with your sources themselves, but more often with the IDE having problems with something (maybe a defect file or such).

But the first stop for those errors is Borland's quality central where users report prolbems and bugs with Borladn's IDEs and where Borland also tells what to do and how to fix them (for internal errors it's often a patch to a newer version).

Have you updated your Delphi 6? If I remember correct then there are 2 or more service packs for D6. If nothing of that helps, create a new empty project and drop your current source into it and see if that works.