The specified solution configuration "Debug|BNB" is invalid

In Expression Blend 4, while compiling I get an error saying

The specified solution configuration “Debug|BNB” is invalid. Please specify a valid solution configuration using the Configuration and Platform properties (e.g. MSBuild.exe Solution.sln /p:Configuration=Debug /p:Platform=”Any CPU”) or leave those properties blank to use the default solution configuration.
Done building project “myproject.sln” — FAILED.
Build failed.

Background: At build-time the compiler (no matter if started from Expression Blend or Visual Studio) has to know what the target platform of your code, i.e. the system architecture like X86, 64bit etc.

The problem now is, that a system wide setting of an environment variable called "Platform" seems to override any setting of what Expression Blend uses as target platform, too.

I found some workarounds on other websites and will provide the possible solutions here. Trying one of the two suggestions should help:

• Delete the conflicting environment variable "Platform" in "Control Panel -- System -- Advanced -- Environment Variables". Restart Blend and give it a try (maybe you have to restart your computer to make this work).
• If this does not help: With the registry editor (Start -- Run -- "Regedit.exe") go to key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment and selected the key Platform. Delete the value BNB. If you do not find the specified key, try repacing "CurrentControlSet" with "ControlSet001", this worked for in one case, too. Then restart your computer.

Please give a comment which of the solutions worked.