Is this a bug?

Are there instances you all can think of where doing a header('location: 
$url'); causes a loss of all session data?  I have a case I can reproduce 
consistently where doing a header() refresh or echoing out an HTML page 
with a meta refresh both cause resulting page to lose session.  My hunch 
is that I may not be accounting for some ingrained PHP handling and that 
this isn't a bug but I can't be sure.  

If required, I can submit the offending code but I'll hold off in case 
there is an obvious answer.

-- 
Tony Bibbs          "I guess you have to remember that those who don't
[email protected]  hunt or fish often see those of us who do as      
                    harmlessly strange and sort of amusing. When you  
                    think about it, that might be a fair assessment." 
                    --Unknown