OmniGraffle slower than a dog

Hi,

I purchased OmniGraffle a few months ago and it's been running fine.  Today
though, when I start it up it takes several minutes before the  "Untitled"
window comes up.  Everything I do takes several minutes for a response
(assuming there is a response). I double-clicked on a text box on a simple
page of less than a dozen items 45 seconds ago and I'm still seeing the
spinning color wheel.

I've got 1.2GB free memory, 3.5 GB free HD space, no network connection.
Nothing has changed since yesterday other than I'm not at home on my
wireless network.

I can troubleshoot stuff like this in Linux, but I'm a n00b with OS X.

Any suggestions on what to do or how to trouble shoot the problem?

--

faber