Blocks in AC 2012

Just upgraded to AutoCAD 2012, and I notice a problem with some of the blocks that I've been using for years:

I have several blocks that I use which comprise two other individual blocks. When I explode the block in oder to leave me with the component blocks, one of the remaining blocks is renamed to *E236 (or *E.... another number) and cannot be exploded. What I've noticed is that this doesn't happen if my blocks are scaled with x&y of 1. Anything else, and I get the *E... and can't explode.

Can anyone tell me what's changed between AutoCAD 2010 & 2012 that causes this problem, because it was fine before.

It is an anonymous block. Been this way for awhile.

From Autodesk..

When nonuniformly scaled blocks contain objects that cannot be exploded, they are

collected into an anonymous block (named with a "*E" prefix) and referenced with the

nonuniform scaling. If all the objects in such a block cannot be exploded, the selected

block reference will not be exploded. Body, 3D Solid, and Region entities in a

nonuniformly scaled block cannot be exploded.

Thanks for that, but I don't understand why I never had a problem with these blocks in AutoCAD 2010??? So I guess that means I will have to completely re-think these blocks then?