Google backlinks not working

Are your links transferring keyword strength

[Whitey]

We have around 25,000 pages on several sites with different hyperlinked text phrases pointing to other sites from each page.

Each page is relevant to each other, the PR is 4 to 6 , there are only 4 or 5 outward pointing links per page.

The content is varied.

The link text only shows on the originating sites when doing a Google search. The target site is not benefiting from the unique keywords.

Last year for 4 months we had great results. Then it stopped. Only some of the sites, plus 1 which is separated from the network with minor linking is now pulling some traffic.

For March this year one of the sites roared for 4 weeks, then went down the proverbial plug hole again.

Any thoughts?

And have you had similar problems?