"pull up (8kohm) on data line."

When I said last night that this sounded a bit high I didn't have the reference to hand, but the document you need is Dallas Application Note 148, "Guidelines for Reliable 1-Wire Networks"

It says, "...very early applications information, for example, suggested use of bus pull-up resistors in the 5k range. While this value will work for reasonable, small networks, it cannot provide sufficient pull-up current for large networks. These days, 1k pull-up values ... are the norm"

I suggest reading this Application Note first as it specifically sets out to address errors & misconceptions which appeared in earlier App Notes, and other published & unpublished sources!