Here's the workaround. Note this is a "hack", but it's been tested on multiple systems and doesn't appears to induce any consequences that I'm aware of.
Download a libpoppler7 deb from whatever site you prefer and install it. I've been using libpoppler7_0.14.3-0ubuntu1.2_amd64.deb. No conflicts noted between Natty's installed libpoppler13.
Install gloobus-preview (aptitude install gloobus-preview). I've been using ppa:am-monkeyd/nautilus-elementary-ppa (as he pops open gloobus to reference his logfile ;-) as a repository for both nautilus and gloobus on natty. Can't speak for any other repos.
It will fail installation with a "post.install" message. Read it -- it will tell you where to find the file for the next step (/var/some/thing/or/another/post.installer).
Open the above file in vi and comment out the stanza that references the pixbuffer -- it's the last stanza. Comment out all lines with #'s.
Rerun the installer. sudo aptitude install -f. The installation process should now complete. Press <space> and smile.
I've submitted a bug report on this error and my "hack". No response, but I suspect am-monkeyd is busy with the Elementary OS project just now.
Best,
/tom
2011-05-07 22:00 HRS MDT
A fix has just been committed to the elementary ppa for the above error:
gloobus-preview (0.4.5-ubuntu11~ppa263)
Tested and working as advertised.