This has happened to me a couple of times in the last week, and I wanted to know if it was something I should be concerned about. When I run the recommended deep scan, WebRoot freezes up when it reaches 81% completion. The system events counter will continue to increase, but the actual progress of the scan appears to halt. If I try to run another scan during this time, it will make it to 100% without any problem. If left alone, the scan will eventually unfreeze (although the total scan time may take 6 or 7 minutes as opposed to under 1 minute under normal cisrcumstances). Even when it doesn't freeze up, there often seems to be a "pause" when it reaches 81%.
I also ran a Full Scan to see what would happen. It scanned slowly, as expected, but once it reached about 80% or 81%, it quickly finished and informed me that the scan was finished.
I haven't experienced any other problems on my computer, but I wanted to ask about this just to see if it was anything to worry about. The other times I've run the deep scan (or it's run automatically), it has performed fine and told me that everything is in order.