Thanks for your post, unfortunately this is not a lot to go on. Just to confirm, is your development computer on a 32-bit OS and the other computers running 64-bit OS? SmartAssembly seems to be sensitive to the bitness of the application so perhaps compiling it explicitly for 32-bit if it is loading any 32-bit unmanaged DLLs may help.
Otherwise, the application will need to be debugged and/or checked for binding failures. Maybe your development machine has some assemblies in the GAC that need to be in the GAC and the other machines do not have them in their GAC.
Can you attach a debugger (Windbg, for instance) and check for exceptions in the protected assembly when you run it?