You're exceeding the specs for the length of firewire, which is 4.5M. Check the link supplied:

http://en.wikipedia.org/wiki/IEEE_1394#Technical_specifications

What you could do is use firewire in conjunction with a "repeater box" or a device that basically strengthens the signal and pushes it further on a "long run cable". So 100' is far too long a cable for typical firewire use. check link:

http://www.amazon.com/s/?ie=UTF8&keywords=firewire+800+repeater&tag=googhydr-20&index=aps&hvadid=11633360747&hvpos=1t1&hvexid=&hvnetw=g&hvrand=1105308900526491220&hvpone=&hvptwo=&hvqmt=b&ref=pd_sl_1tfyczfje_b

tada -----Willy Happy