OK, so I have made some progress, but still having trouble.

There are currently two versions of keepass for Windows, 1.2 Classic and 2.19 Professional Edition. See here. The xml export function of version 1.2 Classic does not seem to work with Wallet. When I tried importing that file, the N9 "thinks" for a second and nothing is imported.

With version 2.19 Pro I had more luck. First I had to convert my .kdb file to .kdbx by importing in Keepass 2.19, then I exported as an unencrypted xml file with the filename "keepass.xml" and imported that into Wallet.

However, all the groups have disappeared in Wallet - everything is file under a group called "Other". Furthermore, the database is full of duplicate items, and each duplicate has retained different fields from the original. For example, where I originally had one entry called "Citibank" which had both the URL and my username and password, now I have two entries called "Citibank", and one of them has the URL, and the other one has my username and password.

To verify, I tried re-importing the XML file back into keepass (2.19), and it worked great - all my entries are filed under their proper groups, and there are no duplicate entries.

So something has gone wrong with the import into Wallet.