diff -r e0d6e9bd3ca7 -r bf7ee68962da javauis/lcdui_qt/src/javax/microedition/lcdui/TextBox.java
--- a/javauis/lcdui_qt/src/javax/microedition/lcdui/TextBox.java	Tue Jul 06 14:10:26 2010 +0300
+++ b/javauis/lcdui_qt/src/javax/microedition/lcdui/TextBox.java	Wed Aug 18 09:43:15 2010 +0300
@@ -286,6 +286,9 @@
     public void setConstraints(int newConstraints)
     {
         textWrapper.setConstraints(newConstraints);
+
+        if(!textWrapper.isValidText(getString() , textWrapper.getTypeConstraint(newConstraints)))
+    	          setString("");        
     }
 
     /**