Hello Mark
yes, they can both live happily together and there is no effect on either. CR 2011 does not install any SDKs / assemblies, so no way to get things confused there. And CR 2011 uses it's own v. 14 dlls and would never use v. 13 dlls from CRVS.
In your case, it's actually an excellent idea to install the two side by side and see if you can do the db source switch in the CR 2011 designer - as you are trying to do in the .NET app (the other thread 
).
- Ludek