Hi Hubertus,
could you please try this for the sake of experiment:
Aware IM automatically generates JSP forms in AwareIMRoot/Tomcat/shared/webapps/AwareIM directory
(where AwareIMRoot is the name of the root directory of Aware IM installation)
The name of the file includes the name of the business space and business object, for example:
BASTestDomainTestHarness_tm_Person_13_Main_Default_Administrator.jsp is the form for business object Person in business space TestHarness (testing mode).
Can you open any such file that has invalid characters with a text editor and include the following line right at the top of the file:
<%@page pageEncoding="UTF-8"%>
Let me know if it makes any difference.