Hi, guys.

I need help with very strange issue.

Let me describe it.

I'm developing now some VF Page for Customer Portal. There is a simple button in this page, and its' handler does not execute any DML.

It just collects information and returns to the same page.

So, when I click the button, I totally randomly get one of  two results:

1. Everything works fine, and there is no any warning or exception in debug log
2. I see standard text of Insufficient Privileges exception instead of the page content (though I remain on the same page), and debug log is totally clear – no warnings, no exceptions.

Below you can find the code of handler method

public Pagereference addCnt()
      {
            famAvailable = new List<Selectoption>();
            famAvailable.add(new Selectoption('', '--None--'));
            cntAvailable = new List<Selectoption>();
            for(String fmId : famIdMap.keySet())
            {
                  famAvailable.add(new Selectoption(fmId, famIdMap.get(fmId)));
            }
            mode = 'new';
            Apexpages.currentPage().getParameters().put('sesId', SessionId);
            return null;
      }

Class is created with sharing

I will really appreciate your help.