diff -Naur otp_src_R12B-3/erts/emulator/beam/io.c otp_src_R12B-3_OTP-7464/erts/emulator/beam/io.c
--- otp_src_R12B-3/erts/emulator/beam/io.c	2008-06-10 14:47:22.000000000 +0200
+++ otp_src_R12B-3_OTP-7464/erts/emulator/beam/io.c	2008-08-04 16:52:15.000000000 +0200
@@ -302,13 +302,14 @@
 #endif
     ErlDrvEntry *driver;
 
+    erts_smp_port_tab_lock();
+
     ERTS_SMP_LC_ASSERT(erts_lc_is_port_locked(prt));
     driver = prt->drv_ptr;
     prt->drv_ptr = NULL;
     ASSERT(driver);
 
 #ifdef ERTS_SMP
-    erts_smp_port_tab_lock();
 
     ASSERT(prt->status & ERTS_PORT_SFLG_FREE_SCHEDULED);
     ERTS_SMP_LC_ASSERT(erts_smp_atomic_read(&prt->refc) == 0);
@@ -412,6 +413,8 @@
     prt->status = ERTS_PORT_SFLG_CONNECTED | xstatus;
     old_name = prt->name;
     prt->name = new_name;
+    ASSERT(!prt->drv_ptr);
+    prt->drv_ptr = driver;
     erts_smp_port_tab_unlock();
     erts_smp_tasks_unlock();
 #ifdef ERTS_SMP
@@ -423,8 +426,6 @@
 
     prt->control_flags = 0;
     prt->connected = pid;
-    ASSERT(!prt->drv_ptr);
-    prt->drv_ptr = driver;
     prt->drv_data = (long) drv_data;
     prt->bytes_in = 0;
     prt->bytes_out = 0;