MusicBee won't let me modify tags on certain songs.

[7eod]

http://imgur.com/0nkxuOO

Everything is grey and unclickable.

[Roadrunner]

I don't even see any content (title asf.). Have you selected one track

[psychoadept]

http://imgur.com/0nkxuOO

Everything is grey and unclickable.

As Roadrunner says, there should be something there, even if you can't edit it.  However, the most common cause of uneditable files is that they are read only.  I suggest checking whether that might be the case.