Bet it’s the ID3 tags.
Scroll down Artist or Album to see if you have a whole lot of Unknown.
Or scroll down Music past the first page to Folders and see if they show up.
The Fuze is just too picky about ID3 tags. It likes ID3v2.3 ISO-8859-1 tags best. It will read ID3 2.2 as well. But it can’t read ID3v1 or, as far as I know, ID3v2.4. And Realplayer may well be using those.
If you can change the Tag version in Realplayer settings, try it. It may not offer that option–iTunes doesn’t.
The best thing to do is make the tags Fuze-friendly and then drag-and-drop them directly onto the unit. I have no idea if Realplayer monkeys with the tags, but it might.
If you can’t find a Realplayer setting, then get mp3tag. http://www.mp3tag.de/en/ It’s free.
When you install it, let it add itself to Context Menus.
Open it, go to Tools/Options/Tags/Mpeg and make Write ID3v2.3 ISO-8859-1. (ISO-8859-1 is the English/Roman alphabet as Windows renders it.) Make sure you save that so it’s the default.
Then, when you get a new album, right-click on the folder and choose mp3tag to open it. Highlight all the tags and just Save them and they’ll be ID3v2.3 etc.
Try fixing one of your problem albums on the computer with mp3tag and make a little change in the folder name–like put an extra hyphen between Artist-Album so it’s Artist–Album or whatever. (Make that change so the Fuze thinks it’s a different album when it goes back.) Then delete it from the Fuze, send it over again from the computer, and see if the tags were the problem.