Lookup with special character

Just a strange thing, at this moment we have an intranet running on Domino.Within this you can switch to another department (java script). This works well until you choose a department with a special character like ñ or so.

The strange thing is that it does work on a R5 server without any problems.

All the region settings and character sets are the same…

Does anyone seen this problem before or can tell me what changed in this part between R5 and R6 ??