problem with e newsletter

when i send a newsletter?i have this error?Warning: mysql_real_escape_string() expects parameter 1 to be string, object given in /www/docs/ on line 774

Warning: Cannot modify header information – headers already sent by (output started at /www/docs/ in /www/docs/ on line 934

i try with a simple texta as content in a wp 3.2..1 with no plugins activate