4.0 Installation problems

I am trying to install OpenBSD 4.0 on a Dell OptiPlex 745. The computer has a SATA CD-ROM and a SATA hard drive.

The install appears to go okay, but then it hangs after the file sets are copied. It doesn't matter if I select all, some, or the minimal file sets: the installation always hangs after the copy is finished. I tried a separate set of CDs, just to see if that was the issue, but I get the same result.

I have no idea what's going wrong. Can someone point me in the right direction?

TIA,

Chris