This afternoon I have upgraded my Wii firmware from version 4.2e to 4.3e. Now i can use the Wii shopping channel again. Also the pre-installed Homebrew Channel (version 1.0.8) and my free developed and downloaded games are still working fine. So i am a happy man!
Important: You have first to upgrade the Homebrew Channel to 1.0.8 before upgrade the Wii Firmware else the Homebrew Channel will be deleted during the Wii Firmware upgrade.