A warning was generated from the assembly-creation phase of the compilation.
If you are building a 64-bit application on a 32-bit operating system, you must ensure that 64-bit versions of all referenced assemblies are installed on the target operating system.
All x86-specific common language runtime (CLR) assemblies have 64-bit counterparts (every CLR assembly will exist on all operating systems). Therefore, you can safely ignore CS1607 for CLR assemblies.
You can ignore this warning if you encounter it when you create a AssemblyInformationalVersionAttribute. The informational version is a string that attaches additional version information to an assembly; this information is not used at run time. Although you can specify any text, a warning message appears on compilation if the string is not in the format that is used by the assembly version number, or if it is in that format but contains wildcard characters. This warning is harmless.
For more information, see Al.exe Tool Errors and Warnings.
This same message ID can be generated under Visual Studio 2008 SP1 with the above message text, Here's a better interpretation in that case:
An assembly created by using the AssemblyCultureAttribute attribute was referenced in creating the current assembly. The AssemblyCultureAttribute attribute indicates the file is a localized satellite assembly and it is not appropriate to reference a satellite assembly. You should probably reference the main parent assembly instead.
In practice, this may mean you should remove the AssemblyCultureAttribute from the referenced assembly.