Multiple Copies Of Vuze Running
Having more than one copy of Vuze running in a given user, both reading from/writing to the same set of configuration files is not going to end happily-ever-after, so from version 5613_B16 detection of this situation was added and secondary instances of Vuze will now refuse to start.
Detection is via a 'lock file' that exists in the Vuze configuration folder named '.azlock'. When Vuze starts it attempts to gain exclusive access to this file and locks it while Vuze is running. Subsequent launches of Vuze will fail to obtain this lock and refuse to start.
If you are getting this error and believe that no other instance of Vuze is running (check for processes that may still be running but not visible) then you can attempt to manually remove the lock file.
If you really want to disable this behaviour then there is a startup argument you can supply to do so:
On Windows you can also specify the argument using the .vmoptions file - see VM Options File. Remember to prefix the argument with "-D" as required by the options file format.