Hey,
Im working on a full body and my computer started lagging at 4 leves... I reopened it and before adding levels I removed selected everything but the head and then added the 4 levels... I added detail and it was very smooth and great but I then tried to get the body back and saw 2 problems.
1. the body wasnt smoothed at the same levels as the head
2. a bigger problem as some of the polys were deleted or not there.
is it possible that the cause is that i saved the file in its remove selected state?