Hi Andrzej,
This problem usually occurs when applying template for a UI in BPM process.
When you select 'Apply Template' and select the data objects and the task, the studio will ask you to specify the Web Dynpro DC where the component needs to be created. Try creating a new Web Dynpro DC for your new component. This is the most common problem faced while applying template. Try keeping the names of the components and the DCs unique to avoid conflicts.
A few other issues also come up related to the studio. Please post the full error stack trace so that we could look at the problem closely.
Regards,
Sid