Poor ranking when linked from 2 "homepages"

is this a bug?

[Namaste]

My homepage is PR6 and another page, which is listed under an additional caregory in Dmoz is also PR6.

2 months back I gave some pages links from the 2nd PR6 page, and instead of rising, many of these pages have suddenly fallen to the 40s,50s and 60s. Their PR is showing as 3 when accessed from the additional PR6 page. Otherwise their PR shows as 4.

Is this is a bug, or am I missing something?