"library routine called out of sequence" error

Hi,

    I have threads in my program that uses the same connection to my
database. In my code, to execute a database query threads have to
acquire a lock first. That is two threads cannot execute a query at
the same time. But I face this error after some time I begin to make
queries. I compiled sqlite with the option
"--enable-cross-thread-connections". It didn't do anything. I thought
there can be a bug in pysqlite. Has anyone faced this error before and
found a solution to it ? I will try using different connections.

pysqlite 2.3.3
sqlite 3.3.12
slackware 11.0