viewstate - datagrid - intermittent error....help

[deevoy]

Hi-
I'm developing a asp.net web application and everything has proven fine

on the dev and acceptance environment.
We've moved the code up to our windows server 2003 prod environment and

get the following intermittent error when browsing the web page through

a client browser (the action causing this is paging though a datagrid-
although it randomly errors, rather than erroring all the time):
________________
Invalid character in a Base-64 string
at System.Convert.FromBase64String(String s) at
System.Web.UI.LosFormatter.Deserialize(String input) at
System.Web.UI.Page.LoadPageStateFromPersistenceMed ium()
________________
However if I run the application on the server itself I never get this
intermittent error. Whilst it is a load balanced environment I've
directed (within my host file) the browser to hit a specific server.
Also for good measure I've set the following:
enableViewStateMac="false"
within the page in question.
Does anyone have any ideas on what is causing this. The intermittent
nature makes it all the more confusing.
many thanks
devo

[deevoy]

Just one more bit of info- I mentioned that this error didn't occur
when running the browser on the server. I've just discovered that the
error does not occur when running accessing through a browser from
home. Hence the only time the error occurs is when I'm running the site
through a browser at work.
The web servers live in our DMZ and at work I access it behind the
company firewall.
Is this making any sense?

One other thing the viewstate is rather large at 16kb.

thanks
devo