Hi,
Without seeing the full data from paypal it is difficult to know exactly what is null. I know that about 7 weeks ago I fixed a bug in the webstore ipnhandler to prevent a null reference exception if the mc_shipping param was missing in the post.
ie the original code was like this:
payPalShipping = form["mc_shipping"].ToString();
but someone reported an error happening there because the form variable was not present so the code was changed like this:
if (form["mc_shipping"] != null)
{
payPalShipping = form["mc_shipping"].ToString();
}
the strange thing was that I never had this exception occuring on my site and I do most of my business through paypal.
from what you posted it looks like mc_shipping is being posted so it isn't clear to me which param is missing, but all I can guess is there is one missing that we are expecting and not checking for null so this error is happening.
I know that in my paypal settings I have it configured to require a phone number, possibly that setting makes it post more things and would explain why the error never happens on my site, but I'm only guessing.
Hope that helps,
Joe