I suspect there is a function in your installation that is "shadowing" some other MATLAB function used by clustergram. I would try to diagnose the problem using the debugger. For example, if you type dbstop if caught at the MATLAB prompt before running your code, you should stop in the debugger at the point where the error occurs. (After you're done, you might want to type dbclear if caught to turn off this feature.)
At the point where the error occurs, you can see what function is getting called. I would then make sure you're using the expected MATLAB function by using the which command. For example, if the line of code is calling a function linkage, enter which linkage at the command prompt, and check that the output points to a function located in your MATLAB installation directory rather than in some other folder. If that's still the case, take a look at the contents of that function file to see if it has been modified.
If you identify the conflict, would you mind sharing the details here? Since other customers have seen similar problems, I'd like to know if there's some relatively common confict we should be aware of.