Delay with check disk dialog

When I try to use the check disk dialog (right clicking a
drive/properties/tools/error checking) the UAC dialog comes up - to which I
click OK, but the CHeck Disk box itself (the one with the two checkboxes)
hangs for about 10-20 seconds & won't register mouse clicks to buttons or
the checkboxes?

It does not say (not responding) in the titlebar - simply hangs.

Any idea what causes this?

Vista Ultimate SP1 - all patched up
Using the Intel AHCI drivers against Seagate 7200.11 sata drives & a
Gigabyte GA-X38-DQ6 motherboard (on both the intel & jmicron controllers)