1. Discard the change set from your repository workspace (say it is in 'component 1'). Your discarded change set now shows as incoming since it is still in the target stream.
2. Make sure that your component 1 in your repository workspace is now in the state you wish the target stream to return to - aka, you have no compile errors, etc.
3. Select component 1 in your repository workspace, in the pending change view. Right click > replace in 'name of your stream here'. Click OK to confirm.
4. Your repository workspace and target stream are now identical, your change set has been removed from the stream.

You can also see our Source Control FAQ "How do I remove a change set from a stream" at https://jazz.net/library/article/126#How_do_I_remove_a_change_set_fro . Look for the second method (see 'You can also discard a change set from the stream by replacing the component') since in your case you don't just want to create a second change set that reverses your first change set but actually remove that change set from the history of the stream.

Let us know if you need more details, your stream should be back in shape in no time :-)

Christophe Cornu