I have the same artifacts on some textures under Windows platform with ATI Radeon 9250 card. For example when scaling texture created from 96x96 png image, or when rotating texture created from 186x186 png image. Also I have another issue with this video card and with non-power-of-two textures mentioned here http://bugzilla.openedhand.com/show_bug.cgi?id=1102
The same textures looks good on GeForce 7300GT for example.
