When I select "Download CD covers..." if either the Artist or the title contain an apostrophe the search replaces the apostrophe with a space, and generally finds nothing.

for example
Artist: Ned's Atomic Dustbin
Tiltle: God Fodder

When you open up the "custom query" it shows:
"Ned s Atomic Dustbin God Fodder"
result is cover not found.

If you edit the query to add the apostrophe back in
"Ned's Atomic Dustbin God Fodder"
the cover is found.