When a secondary (sdb) unpartitioned disk is in the system, a popup window is opened saying that the disk can't be opened (top-left of the screen). Cancel on this window doesn't work and there is no chance to partition the disk afterwards. The install (on the first disk) proceeds normally.
This also occured for me on a new (non partitioned) ide drive. I then used fdisk to put an empty partition on the disk and proceeded with the install. However, the popup panel ("unable to open /tmp/hdb - unrecognized label") did not go away. Pressing cancel did nothing.
fixed for beta2