Don't panic
I have this happen sometimes for no reason. The first thing I do is to re-install Opus.
If that doesn't fix it, then try resetting the registry settings by
clicking the icon to launch Opus, as soon as you have clicked the Icon hold down the CTRL and ALT key.
(Don't press the keys until after you have clicked the Icon.)
You should get an option appear to delete the registry settings; say YES.
I think this should fix the problem---if not then a complete un-install may be necessary before installing again.
If you are using Windows Vista....it could be a compatibility problem.
Some people suggest that if you have too many publications open at one time it can cause problems like this.
You should be able to phone Sales at DW...place an order for Opus 6 and they will e-mail a download link very quickly.