Error closing prepared statements

[Tom Percival]

Hi

I am getting the following very useful Warning from PHP:

PHP Warning: Unknown: Error occured while closing statement in Unknown on line 0

I have traced this through here:

http://lists.mysql.com/commits/29280

to a problem with mysqli_stmt_close:

http://dev.mysql.com/doc/refman/5.0/en/mysql-stmt-close.html

issuing a CR_UNKNOWN_ERROR

This is happening during a period of very high server load (potentially a large blocking query).

My hope is that I can tweak an internal mysql setting or buffer pool size to prevent this from happening but I have hit a wall in terms of what I can find online. Can anyone point me in the right direction or help explain what might cause a CR_UNKNOWN_ERROR?

Many thanks

Tom