Software has nothing to do with it. Sounds like your confusing deadlocking with this (deadlocking = threads trying to access the same resources at the same time)
What BX is talking about is routing tables.
If you have a spanning tree loop you will end up with each router constantly flooding the network with packets saying "im the right router" and end up with a constantly updating route table. No packets will ever get delivered and youll have a crap load of arp packets flying around.
If you want to learn some decent network topology gubbins I would be quite happy to pm you a link to a lecturers notes however they wont make much sense without the talk that accompanies them.
Madmax: Youve said what im saying
the max is not 3.
lol.