Debian Configuration :: Nvidia-kernel-source Was Not Built Successfully

Squeeze-beta was my first foray into Debian, and I love it. I changed my setup to a rolling setup with testing (Wheezy), and have done that for several months. Lately, I got a new kernel, but it reboots to a terminal rather than GUI (I'm a simple laptop user). I think it's because of the NVIDIA drivers, and here is what I've tried (meanwhile, I'm using the previous kernel):

# apt-get install module-assistant nvidia-kernel-common
# m-a auto-install nvidia-kernel${VERSION}-source
A blue screen appears that says:

module-assistant error message Bad luck, the kernel headers for the target kernel version could not be found and you did not specify other valid kernel headers to use.

You can try:

module-assistant prepare
or
apt-get install linux-headers-2.6.38-2-amd64

I have done both, rebooted, and I still get the blue screen. I also see this message:

nvidia-kernel-source was not built successfully, see:

/var/cache/modass/nvidia-kernel-source*buildlog*

...and I have copy/pasted the file below (which omits lines 101-200 because this message is too long then):

/usr/bin/make -f debian/rules clean
make[1]: Entering directory `/usr/src/modules/nvidia-kernel'
test -f debian/control || cp debian/control.template debian/control

[code]....