Lost connection to MySQL server during query

Hi,
this select, which is from Vocabulary Index module:

SELECT distinct(n.nid) FROM term_node t INNER JOIN node n ON t.nid = n.nid WHERE n.status = 1 and t.tid = 2 and n.nid not in (-1,3);

results in:

ERROR 2013 (HY000): Lost connection to MySQL server during query

if I remove the -1, like:

SELECT distinct(n.nid) FROM term_node t INNER JOIN node n ON t.nid = n.nid WHERE n.status = 1 and t.tid = 2 and n.nid not in (3);

then it works fine

this query also works fine:

SELECT distinct(n.nid) FROM term_node t INNER JOIN node n ON t.nid = n.nid WHERE n.status = 1 and t.tid = 2 and n.nid not in (-1);

can you please remove the -1 when it is not required, or can you please tell me what could be wrong with my database..
I have only 16 nodes, so performance can't be a problem.