That doesn't make any sense, why do you even use "WHERE" in a insert query?
serial = getPlayerSerial(source)
x, y, z = getElementPosition(newveh)
a, b, c = getElementPosition(source)
dbExec ( server, "INSERT INTO accounts (serial, x, y, z, cx, cy, cz) VALUES (?, ?, ?, ?, ?, ?, ?)", serial, tostring (a), tostring (b), tostring (c), tostring (x), tostring (y), tostring (z) )