InfoPath Dev

I have several infopath forms that uses Web Services-Upadate List Items 
Service top submit data to several sharepoint lists. Until yesterday all of 
those forms were working without problem. I am thinking that one update 
affect infopath and i started to get this error.

Everytime when i try to submit data i get this error.
''''''''''''''''''''''''''''''''''''''''''''
Request failed.
   at Microsoft.Office.InfoPath.MsxmlNavigator.IsValidNode(MsxmlNode test)
   at Microsoft.Office.InfoPath.MsxmlNavigator.MoveToFirstChild()
   at MS.Internal.Xml.XPath.XPathChildIterator.MoveNext()
   at MS.Internal.Xml.XPath.ChildrenQuery.Advance()
   at MS.Internal.Xml.XPath.ChildrenQuery.Advance()
   at MS.Internal.Xml.XPath.XPathSelectionIterator.MoveNext()
   at System.Xml.XPath.XPathNavigator.SelectSingleNode(XPathExpression 
expression)
   at System.Xml.XPath.XPathNavigator.SelectSingleNode(String xpath, 
IXmlNamespaceResolver resolver)
   at ProjectTimeSheetSubmitForm.FormCode.CTRL29_5_Clicked(Object sender, 
ClickedEventArgs e)
   at 
Microsoft.Office.InfoPath.Internal.ButtonEventHost.OnButtonClick(DocActionEvent pEvent)
   at 
Microsoft.Office.Interop.InfoPath.SemiTrust._ButtonEventSink_SinkHelper.OnClick(DocActionEvent pEvent)
''''''''''''''''''''''''''''''''''''''''''''''

When i try to sumbit data in debugging mode of infopath;
It gives the error for this code line:
'''''''''''''''''''''''''''''''''''''''
            confirm = 
MessageBox.Show(root.SelectSingleNode("my:myFields/my:eName", 
NamespaceManager).Value.ToString() + ": The form will be sumbitted to the 
sharepoint, are you sure?", "Please confirm...", MessageBoxButtons.YesNo);
''''''''''''''''''''''''''''''''''''''''

And the actual error is:
''''''''''''''''''''''''''''''''''''''''''''''''''
System.Security.SecurityException was unhandled by user code
  Message="Request failed."
  Source="Microsoft.Office.InfoPath.Client.Internal.Host"
  StackTrace:
       at Microsoft.Office.InfoPath.MsxmlNavigator.IsValidNode(MsxmlNode test)
       at Microsoft.Office.InfoPath.MsxmlNavigator.MoveToFirstChild()
       at MS.Internal.Xml.XPath.XPathChildIterator.MoveNext()
       at MS.Internal.Xml.XPath.ChildrenQuery.Advance()
       at MS.Internal.Xml.XPath.ChildrenQuery.Advance()
       at MS.Internal.Xml.XPath.XPathSelectionIterator.MoveNext()
       at System.Xml.XPath.XPathNavigator.SelectSingleNode(XPathExpression 
expression)
       at System.Xml.XPath.XPathNavigator.SelectSingleNode(String xpath, 
IXmlNamespaceResolver resolver)
       at ProjectTimeSheetSubmitForm.FormCode.CTRL29_5_Clicked(Object 
sender, ClickedEventArgs e)
       at 
Microsoft.Office.InfoPath.Internal.ButtonEventHost.OnButtonClick(DocActionEvent pEvent)
       at 
Microsoft.Office.Interop.InfoPath.SemiTrust._ButtonEventSink_SinkHelper.OnClick(DocActionEvent pEvent)
'''''''''''''''''''''''''''''''''''''''''''''''''''''

 As i told there is nothing wrong with the code, because these forms worked 
perfectly for several months and suddenly something happened and they stop 
working. I didnt change a thing. i do not understand. i need the fix this 
forms asap. Any suggestions.

The failure is coming from: root.SelectSingleNode("my:myFields/my:eName", NamespaceManager).Value.ToString()

The failure is that the node is invalid. Are you sure that it is "eName" and not just "Name"?

Otherwise, I suggest looking at an XML dump of the form causing the issue to see if the field is actually there.

If the field is there, then make sure NamespaceManager handles the "my" namespace for "root" (which ti should if "root" is the main data source).

Ok, in order to see what is going on i just create a new form with only one text box named tbox and one button.

The code for the button is below;

string asd;

MessageBox.Show(asd);

Ok, it should simply show the letters or numbers which i entered the text box. However i get exactly same problem. I remember now this happened before to me after i installed visual studio 2008 express on my computer and i was suspecting to .NET 3.5. Even if i uninstall .net 3.5 , it did not solve the problem and i reformat the machine and it went back to normal. I just figure out that last week all the computers installed .net 3.5 from mic update. I already tried to uninstall .net 3.5 from one computer but i have same problem. So i do not know it is a bug or something. Any ideas?

Ok it is a definitely a .net 3.5 issue because i just use a laptop computer which has no .net 3.5 but has 3.0 and all my forms work fine. Uninstalling .net 3.5 does not solve that problem. Anu suggestions or seen anything like that before?

I have not seen such an issue personally. There could be some other conflict involved.

To revert back without needed to reformat, use System Restore (a feature of Windows Vista and XP).

ok i tried to uninstall .net 3.5 and i also tried to system restore both of them dont work. i really do not know what to do. i just cant reformat 60 computers. right now there is only one computer in the office which is able to run the forms :(

System restore should have done it for you (provided you have a restore point before .NET 3.5 was installed). You cannot just accept the default restore point (which was the last one created). You must choose a different one--go through the list of available ones and locate one that was BEFORE .NET 3.5 was installed.

Assuming you already did this, and didn't just accept the default (previous) restore point, then I don't personally know of another option--though you should definitely ask around before attempting to rebuild your computers. You might also want to contact Microsoft Support directly to see if this is a known limitation or whether there's just some setting you can change or something.