I had the same problem this morning, but with slightly different message...

Msg 22050, Level 16, State 1, Line 0

Error formatting query, probably invalid parameters

Msg 14661, Level 16, State 1, Procedure sp_send_dbmail, Line 478

Msg 208, Level 16, State 1, Server ServerName, Line 7

Invalid object name 'TableName'.

My problem was fixed when I added the 'Use DatabaseName' statement for each select statements in the @query text. Hope that also solve your problem...good luck.