has my site been penalised.

penalised in google

[inogen]

My sites index page has been given a PR5, and yet every other page has got a PR0.

I did use a link farm, although I've probably only got about 13 backlinks from it, none of which show up when I search for link:www... I stopped using it about 5 weeks ago, and deleted all reference to it from the site.

Anyone got any ideas?