Make sure that DOpus isn't in SYS:WBStartup. It might be loading up after the WB. If DOpus/Opus/whatever-it'll-be-called is in WBStartup, move it somewhere else (SYS: would be a good place) snd it'll stop DOpus running.
If it's not there, check for LoadWB.old in SYS:C
If you can't find that have a search for anything that says LoadWB and post the results here, there should be a backup stored somewhere.
Failing that, you could rename the current one LoadWB_DOpus and copy LoadWB from your WB floppy (the WB and Install disks have it in C).