Code-signed assemblies can make application startup slow on certain machines

When a code-signed assembly is referenced by a .NET application, .NET will go out to the Internet to verify its authenticity at app startup time.  Thus .NET may try accessing Verisign or Comodo web sites.

On some machines where no internet connection is available, the application may pause 30 seconds or so for each code-signed assembly used.  This is a confirmed bug in .NET 2.0 by Microsoft.

Luckily there is a fix available that can be installed here:

This should only apply to unpatched .NET 2.0-based systems.

This post by another company also describes the issue in detail and provides some machine-level or app-level things you can do:

Another alternative is to not use Actipro code-signed assemblies.  Our products include both signed and non-signed versions of the assemblies.  The code-signed variations are included in a "CodeSigned" folder underneath the non-code-signed counterparts.

Note that this issue is not something Actipro can control, and the same issue is applicable to any component vendor who provides code-signed assemblies.