[Observium] [observium] graphs and crontab

Sorry if this has been asked already. I have scrolled thru the posts but I haven't come across the answer to my question yet. When I run ./poller-wrapper.py manually it works fine; I get graphing data for most of my devices, and the graphs show up. But if I let cron run it, nothing shows up? What am I missing?

It's a clean build of Ubuntu 12.04, and Observium 0.13.9.4471.

Thanks in advance, any help is appreciated. Yes, I'm a newb. :-)