Jason,

1) Is the bit rate you download the same as the bit rate you execute at?
2) DTR is the signal from the PC that toggles you in and out of the bootloader, look for it toggling when you select "Loader" or "Execute".
3) How did you implement the downloader signalling?
4) Once you get the banner, don't forget you have to erase prior to a new write.

you might download from:
ftp://ftp.dalsemi.com/microcontroller/

MTKbeta.zip

It's a later rev. loader.

regards,
p