2-sided printing freezes printer HP PSC1510

I always print double sided, and I often print 2-to-a-page too, so the
articles I carry around are smaller and lighter, and to convserve trees. I've
gotten used to this and know how to do it, but suddenly my printer won't
cooperate.
It prints the first side of all the pages, and then either the "double sided
printing" window (where I have to tell it to continue) shows up blank, or
doesn't respond when I push the button.
The printer also doesn't respond when I try to cancel the print (or all
documents) and start over (the printer window claims to be "deleting" but
never does, and won't let me do anything else). I have to reboot in order to
do use the printer, and this is always in the middle of a job. It didn't used
to do this, and I don't want to just print one-sided and give up one of my
favorite features, but I guess I will until I figure this out. Any
suggestions on how to fix this? Thanks.