I noticed another thing: some of the movies included in the IMDB "Connections" are linked with the ones you already have in the database but others don't.
... if a movie you know is in your collection is not highlighted, it's probably because there's a duplicate invisible record in your database. That duplicate record might have been created when the movie you're looking at was added because the existing visible record was not found, or it may have existed before and was not found and merged when you created the current record. I suppose most of these issues arise because the program is attempting to maintain these links by matching titles. Ambiguities (like 'Goodbye Lenin' vs. 'Good Bye Lenin') can result in an existing record not being found and a duplicate being created.
I made a test that make me think the problem has something to do with changing title, although this that not explain the case with "La Dolce Vita" except I changed it by mistake and don't remember.
Here's a description of the test:
1. Started the program without any database.
2. Created some custom items and checked the "Leave as they are" option in "Title formatting".
3. Imported a movie (title, url, comment and custom items) from MS Excel ("Amando de Ossorio: el último templario",
http://www.imdb.com/title/tt0366163/).
4. Imported data for the movie from IMDB.
5. Made visible an item from "Connections, Features" ("Tombs of the Blind Dead",
http://imdb.com/title/tt0067500/) and changed its title to "La noche del terror ciego". The "Add Record" window pops up but it only has "Add New" on the list so I click cancel.
6. Imported data for the movie from IMDB.
7. The connections are OK so far. From the first movie made visible a new item from "Connections, Edited from" ("Return of the Evil Dead",
http://imdb.com/title/tt0068232/) and changed its title to "El ataque de los muertos sin ojos". The "Add Record" window pops up but it only has "Add New" on the list so I click cancel.
8. Imported data for the movie from IMDB. The "Add Record" window pops up but it only has "Add New" on the list so I click cancel.
9. The connections are not OK. From movie 1 are both linked . From movie 2 are both linked. But from movie 3 just the first one is linked.
11. Repeated the test without changing movie titles and all links are OK.
12. Added two more movies making them visibles from Connections -again without changing titles- and all links are OK.
I hope this information would be useful for someone.