They both mean the same thing. The only difference is that "The system has been blocked" emphasizes that *someone* or *something* blocked the system. "The system is blocked" is just an observation about the system.

Another point to add to the above comments is that The system is locked, means it is locked at the moment but it is unknown for how long or by whom. The system has been locked, means that it is something which occurred in the past and is still happening at this point in time. Again, it really depends on the speakers emphasis and what he/she is trying to imply in their statement. ~Samantha :)

Both of them are ok. It depends on the context, use the first sentence in general meaning, meanwhile use the second one to emphasize on particular meaning about the problem of the system.