Web archives show generic icon, not thumbnail

There is a preference Media -> Create Thumbnails -> Web Archives. I have this checked (it is checked by default) yet all my web archives show the generic (Finder) icon for web archives.

Thumbnails are only created while adding/creating/importing/updating files. To create/update thumbnails anytime, just select the web archives and use Data > Thumbnails > Create/Update.

Thanks. I tried that but it doesn’t work. The generic icon (for the OmniWeb browser, in my case), remains. I switched the default browser to Safari and that didn’t help.

Which version of Mac OS X do you use? Creating thumbnails for web archives afterwards is only supported on Snow Leopard.

OS X 10.6.7
DEVONthink Pro Office 2.1

Could you please export one or more web archives and send them to cgrunenberg - at - devon-technologies.com? Then I could check this over here, thanks in advance!