undoing failed import doesn't work

[kazuoF]

Here is what I did:

1) I import entries for any standard module (e.g. Contacts).
2) I get an error message because some of the entries to be imported use dropdown values that are not yet defined in the new CRM installation (for example because lead_source_dom has been extended).
3) After that, the entries where the import succeeded are shown in the List View.
4) I select "Undo Last Import".
5) The imported entries are still displayed in the List View, step 4 seems to have failed.

What is origin of this problem and how can it be solved?

[sts]

I'd expect that there is an error message in sugarcrm.log which will help to see what the problem was. In this 'step 4' Sugar tries to remove the elements from the database table (where they had been added to in the former steps) and maybe there was a problem to execute the sql statement to do this.