In my case opening some projects also takes ages (means around 30 minutes) in Vegas 9.0. I have 6GB of RAM and a pretty powerful Intel i7 920. So hardware is not always the problem.
The project contains about 300GB of raw HD material encoded with the lossless Lagarith codec. ProcMon says that what happens is that Vegas sweeps through all files by reading 4096 byte blocks and some 4 byte sections in about 1-2MB increments. For some reason it waits ages between reads, about 5 mseconds: reading through 300GB so takes 300000*5/1000 = 1500 secs. 5 msec is quite much for purely sequential access on a HDD.
Does anybody know a way to turn off this inital scanning? Not sure why it needs it.