myodbc_end really should only be invoked during Windows DLL unload, since it's not connection-specific and not thread-safe either. This bit of brain fade accounts for our bug #185343 and several bugs filed at mysql.com. diff -Naur mysql-connector-odbc-5.1.5r1144.orig/driver/handle.c mysql-connector-odbc-5.1.5r1144/driver/handle.c --- mysql-connector-odbc-5.1.5r1144.orig/driver/handle.c 2008-02-23 12:51:58.000000000 -0500 +++ mysql-connector-odbc-5.1.5r1144/driver/handle.c 2009-01-14 15:55:10.000000000 -0500 @@ -111,7 +111,6 @@ GlobalFree(GlobalHandle((HGLOBAL) henv)); #else if (henv) my_free((char*) henv,MYF(0)); - myodbc_end(); #endif /* _UNIX_ */ return(SQL_SUCCESS); }