I uninstalled and reinstalled MalwareBytes AV - the new update seemed to be odd. BIG improvement after this, and now I can defrag C down to 38%
Running 4GB ram (3.12 in XP naturally), dual core processors. I shut down EVERYTHING non-essential before stacking. I have only 4GB of free space on C, which seems to potentially be the issue - I cannot seem to make DSS use my terrabyte external as the temp locale (even though the post-stacking autosaves go there). Since I am stacking 21 MB (5616x3744) images, this COULD be the issue, though previously it was NOT an issue.
Driving me nuts!
When it's stacking, the progress bars are a blur (processing that fast), and yet it usually runs out JUST prior to posting the result...