I found the culprit - Skype !!
Many times I had the problem that on some pages ( no pattern ) of my sites
some images showed only half or partly after uploading.
So I uploaded again and again. Sometimes I got lucky and everything was there.
Needless to say, I blamed Xara. ( Well, what do you do when you get frustrated )
Sorry Xara, the problem is Skype !!!!
Before I upload now, I shut Skype off - No more problems with uploading