First of all I assume you are generating a CHM file here. If you are the message relates to the map files you are using inside the project. These files contain details of all the context senstitive help calls being used by the application to call specific help topics. In this case it looks like on of the identifiers for the topic's help call is incorrect or invalid. Things to check are that there are no tabs or invalid characters in the map files (e.g. use alpha numeric characters only).
Thanks. I will look out for this. Yes, it was while generating a CHM file.
We were using RH 5 before and moved to RH 9 recently.
I found that we have hundreds of TABs and german Umlaut characters in .h-files
#define Löschen 1234
If these were the cause, wouldn't we have to get a lot more of these warnings?