Treeview Icons problem

[Mbire]

Hi guys, I added icons to an imagelist which i then associated with a treeview control. The original icons have a transparent background and are of relatively good quality pictures, however when i run my system, they look very grainy at the edges and have a blue border around them when they appear in the treeview at runtime. i used the original icon size (16X16) and a color depth of 32bits. Is there something else about this control and icons or maybe is it haunted? Thanks a lot for your assistance. Regards