Vga Patch for my DC doesn't work!

[32_Pistoleta]

First answer is that you patch the game to support VGA or it WAS VGA compatible.
Second: try not to unplug cable - I play on two of my monitors: Sony & Samsung - so Samsung do the same, then I must to OFF it and then ON by power button, but then I begin not to unplug monitir: I first power on my monitor, then insert Boot-CD and power on my DC - when the SEGA logo desappeared the screen goes black - this is your time - insert your game and enjoy.
If you patched the game to support VGA by yourself - then maybe you do something wrong - once I patch the DoA2 to support VGA - and it was the same case as you described - the games is working, there was the sound and VMU shows all the statistics, but no video - check if that's all right in ip.bin (I mean look inside the ip.bin and check is it supports the VGA)