After a random amount of time, I get errors in form of visual glinches when doing this spesific model(2.49b file imported to 2.54, modified, then opened in 2.55)
I tends to happen after I maximize then unmaximize the UV image editor a few times, I have had entire sessions where I only used texture paint, and it never appared.
This bug may or may not be driver related, I sadly lack a different graphic stack to properly test it on currently.