There are problems and then there are the symptoms of problems. Just as many health problems produce a fever as a symptom, multiple problems can cause attachment problems.
That said, this symptom has been know for a long time. The image shows my hair appearing attached to my butt for a really sophisticated look… not. I’ve seen the problem on and off since I came to Second Life™ in 2008. Now I am seeing it again. For three or five weeks the problem pretty much disappeared.
This problem is generally thought to be a timing problem. The information coming from the server is lost or out of order or otherwise arrives in some way that confuses the viewer. The viewer doesn’t figure out that the hair goes on my head. It doesn’t really attach it to by butt. If I walk away the hair is left hanging in space.
This does just happen with hair. I’ve had a foot, hand, bracelet, dress panel, earring, or other attachment suffer this fate.
The simplest fix is to relog. If the relog does not solve the problem, tp to a deserted region and relog again. You want some place where there is as little load on the region server as possible.
If the problem persists, check you connection to the SL servers. See: Troubleshooting your Second Life Connection Problems. Log off while you run the checks not requiring the viewer. Five or ten minutes can work wonders for your connection to SL.
Clearing your cache will likely make things worse, so don’t.
Trying to change outfits or take the item off or replace it, will just confuse things, you and the viewer. Changing worn items while things are borked can make a mess of things. So, don’t do that either.
Some viewers are more sensitive to the problem than others, or at least they seem so. You can try switching viewers. I always suspect that if a change fixes the problem, it was most likely the connection improving while you were logging off and on rather than the viewer change.