ThomasB - 9:48 am on Jun 12, 2004 (gmt 0)

Asja, first of all welcome to WebmasterWorld!

I wouldn't worry too much about cross linking if the sites aren't hosted on the same IP and are somewhat related. But why don't you try to get more external links to the sites to get natural links. I'd also change to a less obvious and unfortunately also less powerful linking strategy. Link from the high PR sites to the low PR sites but avoid any crosslinks.