I don't need this kernel for any reason other than it was part of the dist-upgrade I just did.
I can understand this. And as a temporary workaround I suggest to follow dibl's advice.
OTOH there is no reason the nvidia driver / one of the nvidia drivers shouldn't run even on *your* system.
How do I set the default to boot back to the last one?
I think it is possible even with grub2.
Have a look at /etc/default/grub (using an editor like nano, mcedit as root)
The line "GRUB_DEFAULT=0" is the one you want to edit.
GRUB_DEFAULT=0
The number at the end of this line can be changed to make the highlight bar or selection bar in the GRUB Menu appear automatically on any GRUB Menu entry we like.
0 (zero) tells GRUB we want the first or top GRUB entry automatically selected unless we over ride that selection with our up or down arrow key during boot-up.
Any number greater than 0 (zero) will mean boot entries further down the GRUB Menu will be selected instead.
I am not quite sure how to select an older kernel which is somewhat hidden in a submenue (#1 would be the submenue with the newest kernel selected (?), I assume. Would #2 be the second entry in the submenue or the third entry in the main menue?). Maybe someone can give an additonal hint.
After editing this line you have to run
update-grub
Anyways, in the long run I'd recomment to solve the problem with nvidia and the newest kernel. Maybe the easiest way would be to provide better info about your system/grafics/exact errormessages and asking towo in IRC directly.