When a promissory note has been taken to court and a judgment entered, does this remove the security interest in the property which secured the note?

No, it does not, it means that the security interest in what is secured can now be taken to satisfy the promissory note.

I wouldn't think so. The property in question should still be valid collateral for the note.

Agree as above, now that they have the judgement they can make a motion to take the property used as security.

And of course do other actions