I am have an asp.net page, where a list of products is shown in a drop down. When a user selects an item, corresponding price, available quantity etc. are shown in the corresponding text boxes. I have used ajax update panel to retrieve these information.

This approach seems to work nicely. But sometimes when a product is selected, it takes too long for the price, quantities to change, and sometimes they don't even change. Then I used firebug to see what happened to the ajax request, and I found out that the response that is coming from the server is something like this -

70|error|500|The state information is invalid for this page and might be corrupted.|

I have absolutely no idea what is wrong here.............