fix pascalabcnet/pascalabcnetide#95

VisualPascalABCNET/Form1.cs

@@ -1476,11 +1476,17 @@ namespace VisualPascalABC
             __showhelpinqueue();
         }
 
-        private void miCheckUpdates_Click(object sender, EventArgs e)
+        private void __checkforupdate(object state)
         {
             WorkbenchServiceFactory.UpdateService.CheckForUpdates();
         }
 
+        private void miCheckUpdates_Click(object sender, EventArgs e)
+        {
+            if (!ThreadPool.QueueUserWorkItem(__checkforupdate))
+                __checkforupdate(null);
+        }
+
         private void cmCollapseRegions_Click(object sender, EventArgs e)
         {
             WorkbenchServiceFactory.EditorService.CollapseRegions();