I am seeing the same problem of prolonged wait before scan starts on "Standard Scan" of "All local drives" with the current beta.
That is the only scan I do and I have to say I don't notice that in my last scan on Sunday.
However, I just started it off now and am watching it spin its wheels so to speak waiting for it to get under way and it just has taking 2.5 minutes to get started.
The status under the local disks shows scanning, the activity bar is moving but the scan shows 0% So it may be that I just didn't notice it stall (or the rootkit scan is taking longer than it should) before it truly starts its on-demand scan.
Which although indicates it seems stalled 2.5 minutes for me isn't the end of the world, but it may well be greater for others and it needs investigation by the Alwil team.
The scan is well under way now so I will see if it includes the duration whilst it was spinning its wheels.
Update:
Scan completed in 16:32 which is a little over 4 minutes longer than my normal scan duration. So I don't know if that extra was a) the addition of the 2.5 minutes spent spinning its wheels plus a little because I continued browsing and answering posts on the forums.
So It would seem that my last scan on Sunday didn't suffer this delayed start as it was in a little over 12 minutes. So the suggestion this might have something to do with a VPS update is one that might carry some weight as there are other functions carried out other than simply updating the VPS.
So somewhere between Sunday and VPS 080505-0, as I'm a day behind on VPS updates, as I have had updates set to manual testing something else.