I am having a very difficult time with the content manager in a .dwt I am trying to create.  It says there are blocks in my drawing for files that I can't even find on my computer, and when I drag and drop a block from the content manager, it shows the changes I made in the Block Editor - but when I import the same block, with the same name, from the folder on my harddrive, where the block is saved, it tells me that the block attributes have changed, and I wind up with an older, different, unedited version of the same block I edited (and saved) with the block editor.  It's driving me nuts.  I am going to go out and buy a PC tomorrow and not use AutoCAD for Mac again.  Every time I think I have a leg up and I know what I am doing, I am thrown for a loop.  The MatchProperties command only sometimes works, it's just so unpredictable!