A questionmark after some artists name

Hello, i've been having an issue that i cant seem to solve, i tried searching but nothing comes up...

The thing is that for some reason, on the playlist of my Android Phone Motorola Defy MB525, the mp3 tags for the artists: Macy Gray, Morcheeba, Noisettes, and Regina Spektor, have a "?" at the end of the artist's name.
I don't understand this, it only happens on the phone and with these artist's songs, and this makes the last.fm scrobbling incorrect, meaning it doesn't scrobble to the correct artist, it scrobbles to the artist's name + "?"...

Example: "MacyGray? - Do Something"

I tried everything, wiping the id3 tags, re doing them mannually, doing them with mp3tag, with other editors, tried ripping the song from an original cd with windows media player, downloading the mp3 from youtube, adding the tags directly from the phone's built in player, still, everytime i transfer the mp3 to the phone the artist name shows with a questionmark at the end.

If I edit the tags from the phone, remove the "?" and save it, it doesnt save the changes, it still shows the "?".

It's very weird, if i remove one letter from the name of the artist, the "?" dissappears... but it is obviously still incorrect with one letter missing.. haha! If i write the name again correctly and save the tags, it shows the "?" again... mistery!

This only happens on my phone, with any media player. In the computer, tags show ok, without the "?".

does anyone know how to solve this???
Thanks a lot !!!

So many possibilities.
First: check the tag-types in the strange files. Are they MP3-only? Or have APE-tags crept in? If so, delete them. If you have other types of tags in the files this could explain why it looks like you could not edit them.
Filter the files to see if there are unprintable characters at the end that are then shown as a "?":

"$if($eql($len(%artist%),$len($trim(%artist%))),1,0)" IS "0"
This shows the tracks that have a blank at the end

Then: check the integrity of your files with foobar or mp3val.
Finally: use the "Remove tag" function and rewrite them and see if that makes any difference.

In general: we are talking about the tags TITLE and stuff and not the filename, right?

hey thanks for the answer, i will try those things!
yes, this is about the tag artist name, not the filename, the filename shows up ok, I'll see if i can solve it with your suggestions!