In my document library only users with Full Control group can upload files or edit them, no other user permission levels are working. There are no workflows attached to this library.
Can someone help me out?
What permissions do these users have? It sounds as if there might be an issue with the permissions role the users have. Look in the Permission Levels option in the Settings screen in the Advanced Permissions link of Central administration to verify the permission being used for the affected users grants them the ability to add and edit items.
Is there content approval turned on in this document library?