I have seen this issue before, and it was tied to .mui's then (if i recall the issue was using a gwes mui from 6.1 which lacked some necessary resource for 6.5 to display those smooth tab seperators)
These .muis are from WPC, not PPC build, that may be why.
Recommend comparing gwes, shellres, commctrl, other similar muis to 0409 muis in a resource editor, see if there's any non-language resource in there that differs (like an RCDATA resource or otherwise)
0413 NLD Dutch
http://rapidshare.com/files/234120783/21232-0413.rar - updated