Not clear how your keepassx problem relates to ubuntu one.
But here is how to create a new database in keepassx.
The first dialogue window is just for loading a database if you have "Remember last open file" in preferences.
These preferences are not removed when purging or reinstalling.
If you press cancel then keepassx will load for creating a new database with a new masterkey.
or
You could Backup/move your keepassx config folder.
Copy and paste in terminal....
Code:
mv ~/.config/keepassx ~/.config/keepassx.old
Then start keepassx which will no longer show the dialogue to load a database until you create one.
Bookmarks