First, you all have been enormously helpful so far.
Doing some more experimentation, it seems that indeed it is
GRUB_CMDLINE_LINUX that needs "acpi=off" added to it. I may have had another
problem because it seems that Trisquel didn't want to load correctly if I
didn't use Trisquel's GRUB bootloader. If I used my other OS's GRUB, then I
had to manually append "acpi=off" each time I booted up, as the GRUB file
didn't seem to make a difference no matter what. Once I restored Trisquel's
own GRUB, it seems to work alright.
Second, I was able to update my kernel to 3.5--I had previously tried the
method in the documentation you linked to, but it didn't seem to work.
Installing the package you mentioned for 3.5 worked flawlessly, and Trisquel
now boots with the 3.5 image.
That's two of my three problems solved! The only thing I have left is this
driver issue.
