Help needed with the Media Manager...

I've searched through the forum, but none of the suggestions work for me. The problem has occurred only since we moved the store from our old server to a new one.

We have a store where we sell sheet music and thus every product has an mp3 preview of the piece - https://www.music.ewis.no

Uploading the mp3's is no problem, they show up in the media folder, and if I upload them to a media collection created before the move, it will show up with the other file on the product page. The problem is assigning media collections created after the move, to products. I've created test "Product Music" pages and tried to assign media collections to them, but they don't show up. If I assign the media collection to a product made before the move, nothing will show in the storepage.
Something strange is that when I assign the collection to a new test product, the assignment seems not to "stick" as when I check "Linked Products:" it says 0. If I assigned it to an older product it says 1. Sometimes media manager will list assigned products, sometimes not.
Another thing that happens is that sometimes I'm thrown back to the login page.

I assume something is wrong with my database... can anyone help me?

Fred

If you compare the DB_XXXXXXX settings from your /includes/configure.php file with your /admin/includes/configure.php file, do they match?

They match...

How exactly did you "move" to the new server?

Did you miss any of the steps outlined in this FAQ: https://www.zen-cart.com/tutorials/index.php?article=100

I'm afraid I didn't follow those instructions... I took a full backup of the old server and asked the new isp to restore the full backup so that the store would be just as it was on the old server. It seemed to be an easier solution than the one you have linked to. Some names changed so we had to change the configure.php files and other files (image handler doesn't work by the way), but other than that, the stores seem to work properly.

I will go through the steps and see if there is something I can do.
Thanks so far :)

I used the Fix cache key utility, and it synchronized the database, but it didn't fix the problem. The thing is, even if I might have done things the wrong way, the store seems to function perfectly normal, except this media manager problem and the Image Handler problem.
Is there really not anything I can do with the store/admin as it is now?

If your system is not set up correctly, then your admin sessions may not be working right, thus the logging-you-out problem you mentioned. If that's still the primary symptom you've got, then yes, there's not much you can do until you fix that.