You can have any two versions of SecureBlackbox installed at the same time when they are installed to different folders.

One potential source of problems with the .NET edition is the option to install assemblies to the GAC: this can cause certain problems when .NET loads an unexpected version of the assemblies. This is resolved at the project level by specifying what particular version you want to use.

With the VCL edition, you would need to change the library paths for your project and optionally for the IDE as a whole.