First of all, chamkast seems to have some obstacle (!) to launcg commercial games, I could only get the derivative ChankaEx release to work, and only *after* laaunching it from an admin account.
Also, the casue of failures might also be due to the bios flash file (dc_flash.bin) and the real/virtual gd-rom/cd belonging to different regions. I could not get soul calibur to work until I did this (to reduce huge mess):
I unzipped the nullDC (I know you use chankast) into three separate folders; bios-j, bios-u, and bios-e. I then hacked the dc_flash.bin and created one dc_flash.bin for each region which I placed into appropriate "bios-X/data" folder. Then I used the japanese region installation of nullDC (in folder bios-j) for soul calibur (becasue the SC I dl'ed is japanese) and had no problems launching ever since.
If you want to know how to hack the BIOS flash (dc_flash.bin) read this post: http://snesorama.us/board/showthread.php?t=32711
Read the paragraph titled "Emulation Notes:" in MOon's post. It's really easy.
For convenience I include the paragraph here:
Do not attempt to burn this. This is a complete GD-Rom dump of the game.
No normal CD/DVD writer supports it. If you want to run this on real
hardware follow the Echelon ripping guide. In case you're wondering, ripping
this game may result in data loss. Currently, only 2 emulators support
complete dumps - NullDC and Makaron. No boot disk needed. Dunno 'bout
Makaron, but to make this run on NullDC make sure your dc_flash.bin is the
correct for the game's region (PAL in this case). You can change the region of
your dc_flash.bin by opening it with some hex editor, going to pos. 0x1A002
and changing it's value to:
0x30: Japan region (NTSC, Orange swirl),
0x31: USA region (NTSC, Orange swirl),
0x32: Euro (Pal, Blue swirl)
Not too far the same string (y11Dreamcast; y is 0,1 or 2]) repeats. Change
there too. To run the game, just use the image plugin and select the *.gdi