"Older posts" has gone missing...

Hi there,
The other day I tried out a plugin, didn't like it, so I deactivated it and deleted it. Itdid some funky things to my site, though. I had to reset the permalinks to get everything to work properly, and that seems to have done the trick. Except that, there is no longer a link at the bottom of my posts page for "previous entries" or "older posts."

Is this something I can fix by pasting in some code? I have a copy of the original files, but I'm not sure what to look for, or where.

Thanks!
Laurie

BTW, the site is http://agriculture.gbiportal.net/