Error with classifier (boost): tlsKey != TLS_OUT_OF_INDEXES in function cv::TlsAbstraction::TlsAbstraction

Hello everybody, I use mexopencv in Matlab in order to use OpenCV functionality. I use a classifier (boost) that I call many many times. Unfortunately, from time to time (usually after days/weeks and many thousands of classifier calls), I get an erratic error from OpenCV. The error that shows up is What() is:C:\builds\master_PackSlave-win64-vc12-shared\opencv\modules\core\src\system.cpp:968: error: (-215) tlsKey != TLS_OUT_OF_INDEXES in function cv::TlsAbstraction::TlsAbstraction Does anybody know what does it mean? How can it be prevented? What is the source of the error?