%1 is not a valid WIN32 application

Customer Environment Windows Server 2008,iis 6.0.

Site configuration is not the same as in the past, "%1 is not a valid WIN32 application" error after updating the class library, such as:

The system login page can load normally, during the login process, this exception occurred, baffled.

Check the data at home and abroad that is the DLL release target cpuX64 and X86 problems, according to the method after the exception remains.

So the assumption is not IIS configuration or 6.0 of its own bug, compared to other version of the environment does not have the same problem, in the site ". NET compilation" In the default language settings from VB to C #, and then visit the site exception disappears, repeated retries to confirm that the setting has a direct impact on the occurrence of the exception, But there is no difference in other site settings Why is there a problem with this site alone?

The root cause has not been found.

%1 is not a valid WIN32 application