--- samigo-app/src/java/org/sakaiproject/tool/assessment/jsf/validator/FinQuestionValidator.java	(revision 26695)
+++ samigo-app/src/java/org/sakaiproject/tool/assessment/jsf/validator/FinQuestionValidator.java	(revision 26696)
@@ -47,7 +47,9 @@
 	
 	public void validate(FacesContext context, UIComponent component, Object value)
 			throws ValidatorException {
-	
+
+		try {
+
 		String text = (String) value;
 		text = text.trim().replace(',','.');  // in Spain, comma is used as a decimal point 	 
 		
@@ -94,7 +96,12 @@
 			i = text.indexOf("{", i+1);
 			if (j+1 < text.length()) j = text.indexOf("}", j+1);
 			else j = -1;
+
 		}
+
+		} catch (StringIndexOutOfBoundsException e) {
+			// string index error
+		}
 		
 	}