Created totally new document in Normal style. Tested -- found Ctrl+B misbehaved just as always. Did Print/Key Assignments. Ctrl+B reports: "Bolders [sic] the paragraph between the indents"
Opened the document I was working on when this problem first manifested itself the other day. Key Assignment report shows identical thing for Ctrl+B.
HOWEVER -- when I went to File/Options/Customize Ribbon/Keyboard shortcuts, I found Ctrl+B assigned to a "bold" macro, not the Home "bold"
Removed assignment. Went into macros and changed name of "bold" macro. Went back to document -- Ctrl+B now behaving. Created another new document. Ctrl+B behaved!
SO -- even though the key assignment printout didn't show there being a macro involved, your comments led me to check that other document, and find it to have been the culprit. So -- MANY THANKS!