Thanks for the replies, everyone. The computer has 6600 quad processor, 8gb RAM, 5 x HD with 2 joined in raid 0. Total 4Tb. All HDs are standard 7200 spin, and not green. Windows 7 pro and Vegas Pro 10d. Haven’t loaded 10e as all is fine with 10d, unless someone tells me otherwise.
The delay wasn’t huge, just 15 secs or less, but it intrigued me. John has hit the nail on the head I think.