Can't select block for in-place editing

I couldn't save one of the blocks after in-place editing (doing some hatching in it) - was getting message similar to below. I deleted all hatches out of the block, and was able to save it. But now I can't select it for editing - get this message:

Command: _refedit

Errors found in references to other objects:

** Object reference missing: AcDbLine, to AcDbHatch.

** Object reference missing: AcDbArc, to AcDbHatch.

*Cancel*

Any ideas?

And how do I remove from the .dwg, blocks whose contents are long since deleted, but their name is still showing as nested in another block, and as not available for purging? Is there a remnant? Can't find the phantom block with QuickSelect.

First post above - seems to have cured itself by rebooting - or perhaps just by closing and reopening the .dwg. I needn't have deleted all my hatching work!

Still my question in the second post.