Thanks for the quick response.
This morning I figured out that the import procedure works very well with the latest Win-Xp release.
Even with an "no error" report (same bookmarks).
On my Win-7 system I get beside the missing folders two errors: "Brauserchronik fail" and "Session fail".
So this is not an Opera issue rather than an issue due to my Win-7, 64bit version.
Ulli