I can only offer a stab in the dark, as I no longer use Outlook and I've never used Lotus Organiser but as no-one else seems to know any better.....
I seem to recall that Outlook could import from a small number of address book formats and Organiser was not one of them. However, Outlook can import what is known as a flat-text file (basically all the codes stripped out of the address book and the various bits of data separated by commas).
See if Organiser will allow you to export a file in flat-text (comma-delimited) format and then try importing that into Outlook.
Best I can do.
Cheers