I guess this is not a XenForo bug (that's why I am not posting it in the bug forum), but a Chrome one (searching on Google learns that much more people have these kinds of problems in Chrome): lately I keep being 'logged out' out of XenForo everytime I re-start my Chrome browser. Automatically logging in doesn't work anymore.
The strange thing is... my vB 3.8 powered website doesn't seem to be affected.
More people have problems with Chrome and it's cookies?
I already tried all that, that's why I thought of posting it here, because still my vBulletin 3.8 site is not affected, but I keep getting this problem on Xenforo.com (after cleaning out everything in Chrome a couple of times now).
And... ... even typing about:cache in the URL and then press Ctrl-Alt-Delete and delete everything does not help. Again, only Xenforo.com is affected and the rest of the sites I use, work without problems. Strange.