Problems adding files to Sansa Clip+: calling all clip experts!

Sometimes, when I add a file to my clip+, it doesn't play. The file will be listed, but will immediately be skipped over when I press play. Sometimes this happens for an entire album, or worse, an entire artist. It will just skip over each track for the album or artist until it has cycled through all the tracks.

I don't know why this happens or how to resolve it. Sometimes, I'll try to add the file again and it will work. Strange. I rip all my music using the same format and size.

Another issue I'm finding is that when the clip is updating after adding music, it will not show some of the files I used to have on the player. If I connect it to my computer, it shows the files, but when I try to find them on the player, they do not show up. Sometimes I'll eject and reinsert the micro sd card, and that fixes the issue, but sometimes it doesn't. It's very frustrating.

I feel like I don't know much about my player. After browsing this site, I feel like I may be missing something important.

What is MSC mode and how do I ensure I am running it?

Is there something I need to do to ensure my micro SD card is formatted properly?

Finally, this may not have anything to do with my issues, but how do I "rockbox" my player, and what improvements will that provide?

Edit: ok I've read up on rockbox, maybe that would help with the issues I'm having?

Nope, I use the same format for all songs that I rip to my computer.

Its strange the way this thing works. Sometimes songs will not show up in my library, I'll eject the micro SD card, re-insert it, and then they'll show up after the player updates.

Sometimes I'll add songs, they'll show up, but the song won't play, just immediately skip to the next file.

Is this a common issue? Will rockboxing it help solve this?