Looks like your disk has problems and WDTV mounted it in read only mode. You should perform a disk check. The plugin saves an moviefilename.imdbid file in the same directory where the movie is. If this fails, it will keep asking you to associate the movie. I fixed that with my new version that caches the imdb ids in /tmp where it will be available till the next reboot. Note that download poster and subtitle will still not work till you fix your disk.
New version uploaded:
- Cache imdb ids and watched status in /tmp.
- If the thumbgen moviesheet cannot be saved on the disk, save it in /tmp to be able to temporary view it.