Why do I get strange or meaningless error messages?
If you installed various versions of Firebird it is quite possible that your client doesn't have the proper message file. The message file holds textual messages for each error code - in case of error, the server sends the code and client uses the message file to give you a meaningful message. However, if message file is mismatched, the index of the message is moved and you get a sensless one.
The message file is named firebird.msg and located in Firebird installation directory. Try installing the exact same version of client as is the server to fix the problem.