Using the latest version of FRD and the Youtube plugin (I have used the check new version and plugins option) I am
unable to download some videos.

Example:

[www.youtube.com]

I hope someone can help

I noticed that when I rename the link to

[www.youtube.com]

it will work....

Yes, the above link points to a user page, and those aren't supported very well.

Fixed parsing of user pages; now you can add a user page link and FRD will download all videos the user has uploaded.