I tried to download a kernel without compact framework. Then I let the VS2005 download the compact framework CAB file. The result is the same: cleared area on the top of the window. I tried your program: splines. It works well. Only the compact framework's software has this behaviour.
I use Hitachi SP14Q006 TZA. The settings:
reg open \drivers\display\Samsung
reg create key mode100
reg set value name string "Hitachi SP14x"
reg set value BFW dword 0
reg set value EFW dword 0
reg set value BLW dword 4
reg set value ELW dword 4
reg set value LPP dword 240
reg set value PPL dword 320
reg set value VSW dword 2
reg set value HSW dword 3
reg set value type dword 0
reg set value config dword 0x00400000
reg set value msignal dword 0
reg set value rows dword 240
reg set value columns dword 320
reg set value width dword 154
reg set value height dword 114
reg set value contrastEnable dword 1
reg set value contrastValue dword 0xeff
reg set value bpp dword 4
reg set value lcdclk dword 2
reg set value EnableCursor dword 1
display mode set 100
contrast set 0xeff
reg save
reboot