diff --git a/hgdriver/hgdev/scanner_manager.cpp b/hgdriver/hgdev/scanner_manager.cpp
index ef264fd..6193aca 100644
--- a/hgdriver/hgdev/scanner_manager.cpp
+++ b/hgdriver/hgdev/scanner_manager.cpp
@@ -103,6 +103,10 @@ void hg_scanner_mgr::clear(void)
 {
     if (hg_scanner_mgr::inst_)
     {
+        {
+            std::lock_guard<std::mutex>    lock(hg_scanner_mgr::inst_->mutex_dev_);
+            hg_scanner_mgr::event_callback_ = nullptr;
+        }
         delete hg_scanner_mgr::inst_;
         hg_scanner_mgr::inst_ = NULL;
     }
@@ -131,6 +135,7 @@ void hg_scanner_mgr::on_hgscanner_pnp(usb_event ev, libusb_device* device, int v
     scanner_handle h = NULL;
     unsigned int len = sizeof(de);
     std::string name(""), type("");
+    std::lock_guard<std::mutex>    lock(mutex_dev_);
 
     sprintf(model, "%x", pid);
     sprintf(vendor, "%x", vid);
@@ -158,7 +163,6 @@ void hg_scanner_mgr::on_hgscanner_pnp(usb_event ev, libusb_device* device, int v
 
         if (index != -1)
         {
-            std::lock_guard<std::mutex>    lock(mutex_dev_);
             bool add = true;
             for (size_t i = 0; i < online_devices_.size(); ++i)
             {
@@ -216,7 +220,6 @@ void hg_scanner_mgr::on_hgscanner_pnp(usb_event ev, libusb_device* device, int v
     }
     else if (ev == USB_EVENT_DEVICE_LEFT)
     {
-        std::lock_guard<std::mutex>      lock(mutex_dev_);
         std::vector<OLSCANNER>::iterator it = std::find(online_devices_.begin(), online_devices_.end(), device);
         if (it != online_devices_.end())
         {
diff --git a/hgdriver/hgdev/usb_manager.cpp b/hgdriver/hgdev/usb_manager.cpp
index 2a4c75a..456f376 100644
--- a/hgdriver/hgdev/usb_manager.cpp
+++ b/hgdriver/hgdev/usb_manager.cpp
@@ -408,7 +408,7 @@ bool usb_manager::get_device_info(libusb_device* device, usb_dev* devinfo)
     devinfo->ver = descriptor.bcdUSB;
     devinfo->vid = descriptor.idVendor;
     devinfo->pid = descriptor.idProduct;
-    devinfo->addr = libusb_get_device_address(device);
+    devinfo->addr = 0;  // libusb_get_device_address(device); - initialize at open 
 
     return true;
 }
@@ -541,7 +541,7 @@ int usb_manager::register_hotplug(usb_event_handler cb, void* user)
     }
     init_notify_thread();
 
-    return 0;
+    return HG_ERR_OK;
 }
 int usb_manager::open(libusb_device* device, usb_io** usbio, std::string* msg)
 {
@@ -614,6 +614,8 @@ bool usb_io::make_singleton(void)
     key <<= 16;
     key |= dev_info_.pid;
     key <<= 16;
+    if (dev_info_.addr == 0)
+        dev_info_.addr = libusb_get_device_address(dev_info_.device);
     key |= dev_info_.addr;
     if (singleton_)
         singleton_->release();
diff --git a/hgsane/sane_hg_mdw.cpp b/hgsane/sane_hg_mdw.cpp
index cea8186..1588672 100644
--- a/hgsane/sane_hg_mdw.cpp
+++ b/hgsane/sane_hg_mdw.cpp
@@ -4,6 +4,7 @@
 #include <time.h>
 #include <fcntl.h>
 #include <sys/stat.h>
+#include <mutex>
 #ifdef WIN32
 #include <windows.h>
 #include <direct.h>
@@ -491,6 +492,7 @@ namespace local_utility
 	static sane_callback cb_ui_ = NULL;
 	static void* cb_ui_parm_ = NULL;
 	static SANE_Auth_Callback cb_auth_ = NULL;
+	static std::mutex	cb_lock_;
 
 	static std::string sane_event(SANE_Event ev)
 	{
@@ -516,6 +518,8 @@ namespace local_utility
 	}
 	int ui_cb(scanner_handle dev, int code, void* data, unsigned int* len, void* unused)
 	{
+		std::lock_guard<std::mutex>	lck(cb_lock_);
+
 		if (SANE_EVENT_SUPPORT_ASYNC_IO == code)
 			return cb_ui_ ? HG_ERR_OK : HG_ERR_DEVICE_NOT_SUPPORT;
 
@@ -556,6 +560,7 @@ namespace local_utility
 	}
 	void stop_work(void)
 	{
+		std::lock_guard<std::mutex>	lck(cb_lock_);
 		cb_ui_ = NULL;
 		cb_ui_parm_ = NULL;
 		cb_auth_ = NULL;
@@ -1085,11 +1090,11 @@ std::string hg_sane_middleware::option_value_2_string(SANE_Value_Type type, void
 		ret = *(SANE_Bool*)val ? "true" : "false";
 		break;
 	case SANE_TYPE_INT:
-		sprintf(buf, "%d    ", *(SANE_Word*)val);
+		sprintf(buf, "%d", *(SANE_Word*)val);
 		ret = buf;
 		break;
 	case SANE_TYPE_FIXED:
-		sprintf(buf, "%f      ", hg_sane_middleware::sane_fixed_2_double(*(SANE_Word*)val));
+		sprintf(buf, "%f", hg_sane_middleware::sane_fixed_2_double(*(SANE_Word*)val));
 		ret = buf;
 		break;
 	case SANE_TYPE_STRING: