Welcome to the bruji forum.
> Go into Preferences (in DVDpedia next to the apple) > go to 'sites', >move imdb to the top of your list. While you are there click on the cog to let dvdpedia know exactly what info you want to harvest from imdb. Job done!
I suspect the reason for some but not all changes after imdb update is because DVDpedia won't replace fields with data already filled in. This is kind of handy when you want to add stuff but maintain the integrity of any info you already have. If you want field entries to be replaced you must delete them.
BTW you don't have to go to IMDB to get no etc, just click on the cog in edit view (Just above the 'OK' button in bottom right hand corner) and choose IMDB - or whatever.