I had an identical problem.
I shrank my extended partition using disk management in windows 7. Then installed OSX on the extended partition (using the nawcom CD which i found out can install on an MBR partition on the fly) after erasing with Disk utility. The install completed, i didn't loose my recovery partition though.
I then couldn't login to windows so i had to use a Windows 7 CD, to launch the c prompt and set partition 1 to active. Then I booted OSX from the nawcom cd and installed chameleon on an SD card and added a few kexts to the SD card.
I was able to update to 10.6.5 but i had to use a modified kernel to boot to OSX.
I already had this kernel in my "Extra" folder before updating so at the boot screen i simply typed "r(0,5)/Extra/mach_kernel" where 5= my OSX partition.
But after boot USB and Networks arent working. So i have to find a way to install the USB kexts from 10.6.4.