If you have any external hard drives they spin down and the browser asks all drives if they are there when you load it.
I had to move all my 2gb external backup powerbooks for this reason as they were driving me insane by taking like 15 seconds to wake up, searched everywhere for a solution but it's built into the drive to be "green" (bah) so can't be turned off. Was almost guaranteed anytime I opened a file dialog or anything that needed to do some disk activity that one of them had spun down.
If you have a floppy drive you can also disable that to get rid of some delay.