DO11: Can't search in Help file

Hello,

don't know what happend. Can't search in the Help file anymore.
In other CHM-files no problems. Any hints?

Directory Opus Pro 11.7 Build 5372 x64
OS 6.1 (B:7601 P:2 T:1) SP 1.0 "Service Pack 1"

Many thanks and greetings
opusfreak

Please give more details. Is the Search tab still there? Do you get an error message? What are you searching for? What happens?