Peggle Nights Deluxe "invalid command line parameter"

[OzLefty76]

I have a legal copy of Peggle Nights Deluxe from the PopCap website, that runs perfectly well from the desktop. But if I try running it in Steam, after recent updates, I get this:

"Invalid command line parameter: C:\Games\PopCap Games\Peggle Nights Deluxe\Peggle Nights.exe"

I don't get it. It runs perfectly well from the desktop - why not within Steam?