Index: reactos/dll/win32/shell32/iconcache.cpp
===================================================================
--- reactos/dll/win32/shell32/iconcache.cpp	(revision 73623)
+++ reactos/dll/win32/shell32/iconcache.cpp	(working copy)
@@ -323,7 +323,7 @@
  * NOTES
  *  appends an icon pair to the end of the cache
  */
-static INT SIC_IconAppend (LPCWSTR sSourceFile, INT dwSourceIndex, HICON hSmallIcon, HICON hBigIcon, DWORD dwFlags)
+static INT SIC_IconAppend (LPCWSTR sSourceFile, INT dwSourceIndex, HICON hSmallIcon, HICON hBigIcon, DWORD dwFlags, HDPA sic)
 {
     LPSIC_ENTRY lpsice;
     INT ret, index, index1, indexDPA;
@@ -341,8 +341,8 @@
 
     EnterCriticalSection(&SHELL32_SicCS);
 
-    indexDPA = DPA_Search (sic_hdpa, lpsice, 0, SIC_CompareEntries, 0, DPAS_SORTED|DPAS_INSERTAFTER);
-    indexDPA = DPA_InsertPtr(sic_hdpa, indexDPA, lpsice);
+    indexDPA = DPA_Search (sic, lpsice, 0, SIC_CompareEntries, 0, DPAS_SORTED|DPAS_INSERTAFTER);
+    indexDPA = DPA_InsertPtr(sic, indexDPA, lpsice);
     if ( -1 == indexDPA )
     {
         ret = INVALID_INDEX;
@@ -374,7 +374,7 @@
 leave:
     if(ret == INVALID_INDEX)
     {
-        if(indexDPA != -1) DPA_DeletePtr(sic_hdpa, indexDPA);
+        if(indexDPA != -1) DPA_DeletePtr(sic, indexDPA);
         HeapFree(GetProcessHeap(), 0, lpsice->sSourceFile);
         SHFree(lpsice);
     }
@@ -424,7 +424,7 @@
         }
     }
 
-    ret = SIC_IconAppend (sSourceFile, dwSourceIndex, hiconSmall, hiconLarge, dwFlags);
+    ret = SIC_IconAppend (sSourceFile, dwSourceIndex, hiconSmall, hiconLarge, dwFlags, sic_hdpa);
     DestroyIcon(hiconLarge);
     DestroyIcon(hiconSmall);
     return ret;
@@ -490,6 +490,7 @@
     INT bpp;
     DWORD ilMask;
     BOOL result = FALSE;
+    HDPA priv_sic_hdpa;
 
     TRACE("Entered SIC_Initialize\n");
 
@@ -499,9 +500,18 @@
         return TRUE;
     }
 
-    sic_hdpa = DPA_Create(16);
-    if (!sic_hdpa)
+    EnterCriticalSection(&SHELL32_SicCS);
+    if (sic_hdpa)
     {
+        TRACE("Icon cache already initialized (another thread got it)\n");
+        LeaveCriticalSection(&SHELL32_SicCS);
+        return TRUE;
+    }
+
+    priv_sic_hdpa = DPA_Create(16);
+    if (!priv_sic_hdpa)
+    {
+        LeaveCriticalSection(&SHELL32_SicCS);
         return FALSE;
     }
 
@@ -556,7 +566,7 @@
         ERR("Failed to create the big icon list.\n");
         goto end;
     }
-    
+
     /* Load the document icon, which is used as the default if an icon isn't found. */
     hSm = (HICON)LoadImageW(shell32_hInstance,
                             MAKEINTRESOURCEW(IDI_SHELL_DOCUMENT),
@@ -582,20 +592,20 @@
         goto end;
     }
 
-    if(SIC_IconAppend(swShell32Name, IDI_SHELL_DOCUMENT-1, hSm, hLg, 0) == INVALID_INDEX)
+    if(SIC_IconAppend(swShell32Name, IDI_SHELL_DOCUMENT-1, hSm, hLg, 0, priv_sic_hdpa) == INVALID_INDEX)
     {
         ERR("Failed to add IDI_SHELL_DOCUMENT icon to cache.\n");
         goto end;
     }
-    if(SIC_IconAppend(swShell32Name, -IDI_SHELL_DOCUMENT, hSm, hLg, 0) == INVALID_INDEX)
+    if(SIC_IconAppend(swShell32Name, -IDI_SHELL_DOCUMENT, hSm, hLg, 0, priv_sic_hdpa) == INVALID_INDEX)
     {
         ERR("Failed to add IDI_SHELL_DOCUMENT icon to cache.\n");
         goto end;
     }
-    
+
     /* Everything went fine */
     result = TRUE;
-    
+
 end:
     /* The image list keeps a copy of the icons, we must destroy them */
     if(hSm) DestroyIcon(hSm);
@@ -604,14 +614,17 @@
     /* Clean everything if something went wrong */
     if(!result)
     {
-        if(sic_hdpa) DPA_Destroy(sic_hdpa);
+        if(priv_sic_hdpa) DPA_Destroy(priv_sic_hdpa);
         if(ShellSmallIconList) ImageList_Destroy(ShellSmallIconList);
         if(ShellBigIconList) ImageList_Destroy(ShellSmallIconList);
-        sic_hdpa = NULL;
+        priv_sic_hdpa = NULL;
         ShellSmallIconList = NULL;
         ShellBigIconList = NULL;
     }
 
+    sic_hdpa = priv_sic_hdpa;
+    LeaveCriticalSection(&SHELL32_SicCS);
+
     TRACE("hIconSmall=%p hIconBig=%p\n",ShellSmallIconList, ShellBigIconList);
 
     return result;